The cancellation of the electrification of the Cardiff to Swansea stretch of the Great Western line was an act of “retribution” by a Conservative Government, according to John McDonnell.

Labour's Shadow Chancellor claims the party was given a bloody nose by voters and is now abandoning Wales.

Jeremy Corbyn’s closest political ally hopes for a second early election and is campaigning in Preseli Pembrokeshire today, where the Conservative majority crashed last month from 4,969 to 314.

The Conservatives lost three Welsh seats to Labour and Mr McDonnell’s ambition is to make Wales a “Tory-free zone” as it was after the 1997 and 2005 elections.

Here are six of his key messages as he works to keep up the election momentum:

1. Electrification shows the Tories are ‘abandoning Wales’

Describing the cancellation of the electrification as “absolutely appalling”, he said: “It demonstrates [for] me exactly what this Government is all about. They are abandoning Wales, basically...

“They have had a bloody nose from the election and in some ways this is retribution.”

He described the way the announcement was made on the last day of parliament in a written statement as a “democratic disgrace”.

He said: “Normally what would happen is that you’d have an oral statement from a minister, normally the Speaker would allow an hour’s questions so you’d be able to tease out the information. Often as a result of that you’d be allowed an Opposition Day to debate the issue...

“No way to run a democracy, is it?”

2. The Swansea Bay Tidal Lagoon should get an immediate green light

The long-awaited Hendry Review gave the lagoon the thumbs-up in January but the Government has yet to commit to the project to harness the energy-generating power of the tides.

Mr McDonnell said: “We are pressing the Government at the moment. If we go into Government tomorrow the Swansea Bay lagoon will go ahead.

“We’d be implementing it immediately... We see it as the most significant development not just in Wales but in the country as well.

“It’s a model for other areas. The risk that there is now is potential disaster...

“The Government’s response has been tepid to frozen. Simple as that.

“We’re pressuring them all the time. They need to make the decision and get on with it now.”

He contrasted the electrification cancellation and the uncertainty around the lagoon with the UK Government’s support for London’s £30bn Crossrail 2.

He said: “We support Crossrail 2 but what you don’t do is you don’t favour London and the Home Counties against other parts of the country... This is a stark example [of] just the neglect of Wales overall.

“It demonstrates where the Tories’ priorities are, and it certainly isn’t Wales.”

3. The £1bn Tory deal with the DUP could fall apart

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“The anger remains,” he said. “I’m really angry about it.”

The Shadow Chancellor said the deal to get the party’s 10 MPs to prop up Theresa May’s administration worked out at “£100m a vote”.

He said: “It’s a pure, simple bribe and what angered me is if they can find the £1bn, why can’t find the equivalent for Scotland, Wales and elsewhere?”

Mr McDonnell predicted the partnership with the Northern Ireland party will become unstable train when the DUP’s own voters feel the consequences of continuing Conservative government.

Claiming the DUP had a “working class base”, he said: “The DUP’s support comes from people who have suffered the most from austerity... They have undermined their own electoral base within their own constituency.”

The first ministers of Wales and Scotland have launched a formal dispute resolution process in a bid to win proportionate funding for their nations, which they claim would lead to Wales receiving an extra £1.67bn.

4. The funding system for Wales is 'patently unfair'

A cross-party report this month called on the UK Government to “bite the bullet” and scrap the Barnett formula which is used to distribute Treasury cash to the devolved governments. Critics claim Wales has been underfunded.

The Shadow Chancellor said: “It’s been a big debate within the Welsh Labour party of late. We’ve said to them when we go into Government there will be a review and we’ll be looking at the fairness of the overall distribution mechanisms.

“Welsh Labour will have a significant voice in that and Carwyn and others have made it very, very clear that they feel the existing system’s unfair. We share their concerns so there will be a review.

“What comes out of that will be shaped by the Welsh people themselves and obviously [there are] issues around Scotland and the rest of England but we can’t go on with a system that is so patently unfair.”

5. Carwyn Jones and the UK Labour leadership are on the 'same page' on Brexit

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Labour has been accused of being split on Brexit, with First Minister Carwyn Jones arguing the UK does not have to leave the single market but Shadow International Trade Secretary Barry Gardiner claiming that a Norway-style deal would leave the UK as a “vassal state.”

Mr McDonnell said there was common agreement that “tariff-free access” was essential.

He said: “If we don’t get tariff-free access it will have a crippling effect on our economy... To a large extent in terms of our objectives, Carwyn and [the UK leadership] are on exactly the same page.

“In terms of the structures, again, this is a secondary issue. We’ll establish the structures that gain us the tariff-free access.

“We’ve said time and time again there’s a willingness among our European colleagues to be extremely flexible. Tony Blair said this two weeks ago – fully agree with him.

“What the Government are doing is they are driving the European negotiators into a corner and as a result of that we think they are risking our economy and jobs. We won’t allow that to happen.”

Flagging up the threat to farming, he said: “We think the overall Government strategy is one which will damage the agricultural sector. And on that basis, we’re just hoping this Government falls as quickly as possible and we can take over.”

6. If the campaign had gone on another fortnight Labour could be in power

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Polls had suggested the Conservatives could win half the seats in Wales but support collapsed as the campaign rolled on.

Mr McDonnell said: “We’ve demonstrated what we can do. We have ambitions to make Wales a Tory-free zone again.”

Mrs May’s gamble of a snap election resulted in the Tories losing their majority but the Shadow Chancellor argues Labour could have won power if the campaign had continued.

He said: “I think if we’d had another week or two we’d be in Government now.”

McDonnell on his Welsh Labour hero

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Mr McDonnell described how he takes inspiration from NHS pioneer Aneurin Bevan, saying: “I’ve said I want the next Labour Government to be more radical than the Attlee Government... The shining star of that Attlee Government was the NHS and that was down to Nye Bevan...

“It wasn’t just determination. People underestimated the ability of the man to negotiate a deal with the doctors and others.

“People are always saying what a fantastic orator he was, which he was. But he had a command of detail, of policy, that other people didn’t as well.

“He had a command of the legislative process... [His] civil servants respected him because he had a command of detail.

“They could never outwit him when it came down to implementation of policy.”

McDonnell on Welsh Labour’s rising stars

Mr McDonnell heaped praise on Torfaen MP Nick Thomas-Symonds, a former barrister who wrote a biography of Bevan.

He said: “Nick Thomas-Symonds is already Shadow Solicitor General. Brilliant.

“You those look at those youngsters who have come in, people like him are fantastic.

“You look at his ability, I tell you he will shine. He’s one of our stars for the future...

“He knows his stuff. He knows his history...

“He understands the movement... He’s extremely intelligent but he combines that with ability.”

Mr McDonnell also put the spotlight on Swansea East Labour MP Carolyn Harris, who came to UK-wide attention with her campaign to get councils to scrap burial charges for children. In March the First Minister announced the fees would go in Wales.

Mr McDonnell said: “She demonstrated that almost single-handedly you can take an issue, transform it into a campaign and win... She’s won the respect of people right the way across the House as well.”

Praising Shadow Welsh Secretary Christina Rees, he said: “In terms the work that she’s done on the ground, she now knows what sort of programme needs to be implemented [and] she’s one of our best advocates.”

Here’s what the Welsh Conservative leader thinks of Mr McDonnell’s ambitions in Wales

Welsh Conservative leader Andrew RT Davies, said: “This is yet more empty rhetoric from a Labour party on the run after being found out for their betrayal over student debt and tuition fees in Wales. It is abundantly clear that Labour’s election promises were pure fantasy and these latest comments are beyond laughable, particularly from the man who’d ruin the country’s finances if he ever got his hands on the Exchequer.

“With Labour in complete disarray – Carwyn Jones and Jeremy Corbyn seemingly determined to contradict each other at every turn on their plans for Brexit – the prospect of them negotiating our future is frightening. And as our announcement to abolish the Severn Bridge tolls last week showed – boosting the Welsh economy to the tune of £100m – it’s clear only the Conservatives will deliver a better and more prosperous future for hardworking people across Wales.”

Brecon and Radnorshire Conservative MP Chris Davies said: “John McDonnell would have been better off stopping at Cardiff Bay to try and agree an actual policy position with Carwyn Jones – then heading straight to Caerphilly to see Wayne David. Banging heads together between his deeply divided colleagues would be more appropriate than going to Preseli on a vanity exercise.”

“Labour in Wales and across the UK have more faces than Big Ben when it comes to Brexit – it just goes to show that whether it is the first minister or other Labour politicians – grandstanding is always temporary. Voters in Wales voted to leave and it is the Conservative party that is getting on with securing the right deal as we leave the European Union.”