The government is to publish economic forecasts comparing Prime Minister Theresa May’s Brexit deal with remaining in the European Union in a major concession to MPs.

The move came after several Tory MPs, including former minister Jo Johnson, signed a Brexit-linked amendment to a Budget Bill in the House of Commons.

Umunna’s amendment sought to force the government to publish economic forecasts to allow the impact of May’s EU withdrawal agreement, remaining in the EU and leaving with no deal to be compared.

Treasury minister Robert Jenrick confirmed the government will provide economic modelling of three Brexit scenarios compared to the status quo.

He told MPs: “I’m happy to confirm the baseline for this comparison will be the status quo – that is today’s institutional arrangements with the EU.

“I can confirm this analysis will bring together evidence from across Government, external stakeholders and a range of analytical tools.

“The analysis will consider the long-term costs and benefits of moving to new trading relationships with the EU and with the rest of the world.

“The analysis will consider a modelled no-deal scenario – or World Trade Organisation terms – a modelled analysis of a free trade agreement scenario, and a modelled analysis of the Government’s proposed deal.”

Umunna, in a statement issued outside the chamber by the People’s Vote campaign, said: “The Government was planning to con the British people.

“It is vital at this crucial time for our country that MPs and the public know the full facts about the cost of Brexit and how it compares to the deal we already have inside the EU.”

Shadow economic secretary Jonathan Reynolds welcomed the concession, but told MPs: “I think, reflecting the parliamentary arithmetic, I’m not sure they did it voluntarily until they saw the names on the order paper.”

Former rail minister Jo Johnson, speaking in support of Umunna’s amendment, said the concession was a case of “better late than never”.

He added: “If we’ve learnt anything from the chaos of the last 30 months, it is that facts are sacred. This is a debate which has been characterised by falsehoods and misinformation from day one.

“It’s extraordinary that we’ve now had to force the Government at this relatively late stage to publish vital information necessary for an informed public debate.”

On another busy day, Tory MPs plotting to topple May are still struggling to muster enough numbers to trigger a vote of no confidence in her leadership.

The putative rebellion against the Prime Minister faced ridicule after it emerged that backbenchers had again failed to get the required 48 names needed to start the process of ousting her.

The faltering rebellion came as May’s crucial Parliamentary alliance with the DUP suffered its first serious cracks after the party voted with Labour on a key Commons vote on the Budget.

In an ominous move for the Prime Minister’s Brexit plans, the Northern Ireland party also refused to support the Government on a string of other measures in the Finance Bill.

The DUP, which has heavily criticised May’s proposals for exiting the EU, flexed its political muscles by abstaining on several votes, including a proposal by Jeremy Corbyn to insert a child poverty test into the legislation.