Renewed efforts to block Brexit were revealed today after a senior Labour MEP was accused of secretly trying to reverse the result and an ex-Tory Cabinet minister returned to frontline politics to join the fight to keep Britain in the EU.

Richard Corbett, Labour's deputy leader in Brussels, was found changing key lines in European Parliament documents.

The MEP tried to water down the significance of June's referendum result by seeking to amend a European Parliament motion.

Meanwhile Stephen Dorrell, the former health secretary who was appointed the chairman of the European Movement campaign group, announced he will create the first official campaign that calls for the June referendum result to be rejected.

Richard Corbett, pictured on the BBC today, Labour's deputy leader in Brussels, was found changing key lines in European Parliament documents

He urged Theresa May to rethink her pledge to trigger Article 50, the formal mechanism for leaving the EU, because it would damage Britain's interests.

He said: 'Brexit is a mistake and we shall seek to build support for that point of view .

'The government has a mandate but I don't think the mandate it has reflects this country's interests, so I will seek to defeat it.'

In a simultaneous plot in Brussels to block Brexit going through, Mr Corbett deleted a line saying that the European Parliament 'stresses that this wish [to leave the EU] must be respected' to saying it 'notes' the referendum'.

Another line opened the way for Brexit to be reversed if there was any move to do so in Britain.

The proposed changes, revealed by the Sunday Telegraph, stated that the European Parliament must not 'stand in the way of any reconsideration by the UK of its intended departure'.

The amendments were proposed in October but rejected by the Brussels Constitutional Affairs Committee.

Labour leader Jeremy Corbyn, pictured, has now come under pressure reassert the party's position on Brexit

Today he distanced the Labour leadership from his decision to table the amendments, describing himself as a 'humble lame duck MEP' who does not speak for the Labour Party.

He told the BBC: 'All I'm doing is stating things that are commons sense - that if, as we move forward, this turns out to be a disaster then we need to look very carefully at where we're going.'

But Labour leader Jeremy Corbyn has come under pressure reassert the party's position on Brexit.

He has repeatedly insisted Labour will not attempt to keep Britain in the EU but has been undermined by senior figures suggesting the party could frustrate the process by demanding certain conditions on Britain's exit.

Former health secretary Stephen Dorrell, pictured, announced he will create the first official campaign that calls for the June referendum result to be rejected

Two dozen Labour MPs even voted against triggering Article 50, the formal process for leaving the EU, earlier this month as they joined Lib Dem and SNP MPs in trying to block Brexit going ahead.

Former Tory Cabinet minister and Brexit champion Iain Duncan Smith said the secret plot by Labour MEPs in Brussels to reverse the referendum result was further evidence of Labour 'ignoring' voters.

Dominic Raab, the former justice minister, accused the party of 'sneaky wrecking tactics'.

Appearing on the BBC1 Daily Politics Show today, Mr Corbett said that if leaving the EU turns out to be bad for the economy and costs jobs Britons might want to vote again on it.

He said: 'Well there are many people, I get lots of letters from people who say, 'well hang on a minute, this was an advisory referendum won by a narrow majority on the basis of a pack of lies and a questionable mandate'.

'But if there is a mandate from this referendum it is surely to get a Brexit that works for Britain without sinking the economy.

'And if it transpires, as we move forward, that this is going to be a very costly exercise, then there will be people who voted leave who will say 'hang on a minute, this is not what we were told. We were told it would save money, we could put it in the NHS, but if it is going to cost us an arm and a leg then I would like the right to reconsider'.'

He said if Brexit is going to be a 'disaster' that's costs jobs then 'it's something we might want to pause and rethink'.

Meanwhile, shadow home secretary Diane Abbott has refused to say if Labour will place controls on immigration.

Senior party figures including shadow Brexit secretary Sir Keir Starmer has called for the numbers to be cut in the wake of the EU referendum vote.

Shadow home secretary Diane Abbott has refused to say if Labour will place controls on immigration

But while Ms Abbott conceded Britons are 'very concerned' about the impact of immigration, she dismissed calls for a control on the numbers coming into the UK as 'scapegoating' immigrants.

Speaking to Sky News's Murnaghan, she said: 'What we believe is if we bear down on exploitation we will bear down on levels of migration, but setting numerical targets has not worked.

'The Tories have done it for six years now and immigration is at record levels, we want to deal with the underlying issues in communities.'

Labour's policy to create a migration impact fund will help ease the strain on public services, while better enforcement of the minimum wage will help prevent the undercutting of British workers, she said.

Conservative MP Nusrat Ghani, who sits on the Home Affairs Select Committee, said the comments show Labour is 'completely out of step with the concerns of working people'.

She said: 'They don't want more control over immigration and keep talking about blocking the decision to leave the EU.