Jeremy Corbyn has accused Theresa May of presiding over “a government in disarray” and declared that the Labour party, revitalised under his leadership, now represents the mainstream of British politics.

Speaking before his party’s first conference since the Conservatives lost their majority, Corbyn said Boris Johnson’s recent Brexit intervention demonstrated that the prime minister had surrendered control of her cabinet.

The Labour leader argued that Johnson’s 4,000-word manifesto represented a lapse of discipline that just “would not happen” in his own shadow cabinet team, which is more united after his party made unexpected gains in June’s general election.

Corbyn added that Labour was getting ready for another poll because of May’s weakened position in parliament, and vowed to unseat a string of senior Tory MPs with reduced majorities, such as Amber Rudd, Justine Greening and Iain Duncan Smith.



“The election has changed politics in this country. We are now the mainstream. The government lacks any sense of direction. They are hiding behind parliamentary power grabs to avoid scrutiny,” he said, vowing to disrupt May’s attempted changes in the Commons.



“We will use our strength in parliament and our support in the country to challenge the Tories at every step. Wherever we can, we will block their attempts to pay for tax cuts for the richest by making life worse for millions of people.”

He added: “It is a government that is in disarray. We will keep up pressure in parliament. There is a social agenda, investment in housing, health and social care and industrial needs … We are ready for an election and we will keep on demanding that this takes place in parliament. That is the process in parliament.”

Jeremy Corbyn in his office with Ian Lavery MP. Photograph: Sean Smith/The Guardian

As the party prepares for the possibility of another election, Corbyn revealed plans to restart his tour of marginal constituencies, with Labour completing selections in 100 key seats by the end of the year.

“We are preparing by selecting candidates in key seats, by putting detailed policy papers together on all aspects of policy; we are preparing by campaigning over the country, continuing to challenge austerity,” he said. “And we have made enormous progress in changing the political debate. The campaign showed what Labour can do when we go out with a message of hope.”



The Labour leader said he wanted to host further rallies in seats held by cabinet ministers and high-profile Tories, listing the home secretary, Rudd, the education secretary, Greening, the Welsh secretary, Alun Cairns, and the former party leader Duncan Smith as big beasts Labour was hoping to oust.

The Islington North MP also promised to relentlessly target Johnson in Uxbridge and South Ruislip, on the other side of London, as he criticised the foreign secretary’s calls for deregulation and tax cuts in last week’s newspaper article.

“It is a very strange set of circumstances when the foreign secretary writes a 4,000-word article for the Daily Telegraph which is essentially a manifesto for destroying workers’ rights, undercutting, damaging all the protections we enjoy,” he said.

Corbyn said it was peculiar for Johnson to be writing articles while May was preparing to give a major speech in Florence about Brexit. “The contents of which we don’t know, but maybe she doesn’t know them either,” he added.

Asked how he would react if a member of the shadow cabinet had behaved like Johnson, Corbyn replied: “They wouldn’t do it.” But what if they did? “They wouldn’t do it. It wouldn’t happen. We would expect and they would consult with my office before it was done,” he said.

Jeremy Corbyn at a rally at the Central Mosque community centre in Glasgow in August. Photograph: Sean Smith/The Guardian

He said Johnson’s blueprint for Brexit proved senior Conservatives were intent on using the UK’s departure from the EU as an opportunity for deregulation, and “special trade deals” with Donald Trump’s America that benefited multinational corporations rather than workers. Corbyn also warned May and Johnson against using Canada as a model for the UK’s future relationship with the EU, highlighting problems with the EU’s Ceta deal with Canada as well as with the Transatlantic Trade and Investment Partnership (TTIP).

“We are opposed to TTIP-style deregulation and investor protection deals with the Trump administration, which is precisely what this Tory government wants to use Brexit for. We want trade based on fairness, open rules and strong rights and protections,” he said.

Despite the political focus on Brexit, Corbyn is determined that Labour should not let domestic issues drop off the agenda, as party members prepare to debate policy at their annual gathering in Brighton next week.

He said pressuring May to scrap the public sector pay cap was firmly in his sights, as the Labour leadership believes the election showed his party have already won the national argument in favour of ending austerity.

Asked if May was provoking strikes by failing to act on public sector pay, Corbyn hinted that she was, by failing to lift the cap and claiming that rises should only be paid for by cuts in public services.

“Austerity has been forced on public sector workers. I’ll be supporting the TUC campaign. I think the public as a whole would be behind public sector workers on demands. Many private sector workers are in work poverty,” he said.

Labour would lift the cap but in the long term would move towards collective sectoral bargaining, where trade unions hammer out agreements on pay with employers.

Jeremy Corbyn in Keswick in August. Photograph: Sean Smith/The Guardian

Corbyn, who will hold a mass rally for supporters on Saturday night, said the theme of this year’s conference would be “the strength of the party” after Labour gained another 3m votes at the election and grew to more than half a million members.

The conference will be the first for three years that takes place without a preceding leadership contest, and with Corbyn secure in his job.

Asked if he felt he had proved MPs wrong after they attempted to keep him off the ballot in a second leadership battle, the Labour leader said he was “very happy in the position we are in”.

Corbyn also promised that rule changes – which will make it easier for a successor to come from the left of the party by reducing the power of MPs – were only the start of what was to come.

He made clear a new democracy commission, due to report next year, was important for “looking at ways in which the party needs to open itself up and ways we need to be campaigning more in the community as well as representative of diversity in the country”.

A Conservative spokesperson said: “Labour’s top team are hopelessly divided. Whether it’s over the basic principles of Brexit, economic policy or on key parts of national security policy like Trident, they contradict each other and backtrack on their promises.

“The simple fact is they’re not fit to govern – and it’s people who would pay the price for that failure.”