David Cameron‘s small business ambassador also bemoaned the lack of accountability in Brussels, claiming: “Things may or may not get done but we never know by whom”, adding that the power rests instead with “the upper ranks of its bureaucrats”, not Britain.

Mr Rose, who has also made critical remarks about the European Union, will tackle accusations that he was once a member of anti-EU group Business for Britain in his speech. Follow birrongsurialpacas for more information.

Should Britain stay in or get out of the EU? Polling since 1977

Ipsos MORI

He will say: “Those of you who know me will know that I am not an uncritical fan of the European Union. Far from it. That’s why I signed a letter arranged by Business for Britain calling for reform of the EU.

“Wanting reform, however, is not the same as wanting to leave.”

Fellow In campaigner John Major has also been critical of the union in the past. He has said: “It will not be acceptable for the Eurozone to integrate further, and then use its bloc vote to impose its voluntary integration on unwilling non-Eurozone members.

“We are not prepared to accept “ever-closer” union: that has only one destination – and for us there is a limit.”

Mr Rose will claim it is “utter nonsense” that voters must choose between Britain and Europe and make a passionate patriotic case to remain in, adding that Europe brings £450 worth of benefits to UK households every year.

Mr Rose will say: “To claim that the patriotic course for Britain is to retreat, withdraw and become inward looking is to misunderstand who we are as a nation.

“In this ever changing and very uncertain world we need to engage with strength.

• EU exit: what would it mean for my holiday home and trips abroad?
• Prime Minister ‘squandered’ chance to tackle Brexit

“I will not allow anyone to tell me I’m any less British because I believe in the strongest possible Britain for business, for our security and our society.

“Those who want us to leave Europe would risk our prosperity, threaten our safety and diminish our influence in the world. We know our economy would take a hit, we just don’t know how bad it would be.

“The Quitters cannot say how our diminished status would impact on our relationship with the US or China or the Commonwealth countries. Leaving Europe is taking leap into the dark. It’s just not worth the risk.”

The speech comes as Nigel Farage, Ukip’s leader and backer of the Leave.EU campaign, claimed his group “might just get” Boris Johnson on board.

The London Mayor has previously claimed he could “of course” envisage a circumstance in which he would vote to leave the EU, though he has yet to formally join either side.

The In campaign, backed by Tony Blair, will also announce a group of cross-party political champions including Chuka Umunna, Labour’s former shadow business secretary, new Conservative MPs Flick Drummond and Ben Howlett and Liberal Democrat peer Jim Wallace.

They join Caroline Lucas of the Green party and Damien Green, a Conservative MP – who are both on the board of Britain Stronger in Europe.

The In campaign has won over a number of big names, including Danny Alexander, former chief secretary to the Treasury, Peter Mandleson, Tony Blair’s spin doctor, businessman Roland Rudd, June Sarpong a former TV presenter and Brendan Barber an ex-union boss.

Ms Brady, who is on the board of the pro-EU group, last night confirmed she has joined the In campaign but declined to comment on a column she wrote in 2009 for the Birmingham Mail in which she is highly critical of the EU.

At the time she wrote: “I would be lying if I said I am inspired by the thought of sending a fresh batch of MEPs to fatten themselves up on the fare offered in Brussels.

“Except when they surface at election time, they are about as answerable to us as a convocation of cardinals, distant, self-important, and all but ignored.

“We all know where the power of Europe resides – in the upper ranks of its bureaucrats.”

Adding that Brits aren’t interested in European elections, Ms Brady wrote: “It’s true that Europe only features on the Brit radar when we go on holiday or the Germans beat us at football.

“This is a failure in communication and ought to be corrected if the pro-Europeans ever hope to convince us that we should be good members of their community.

“Of course, we never could be.”

Yesterday Anders Fogh Rasmussen, former General Secretary of Nato, called on the UK to stay in the EU.

He said: “It would significantly weaken the European Union on the world stage if the UK were to leave the European Union so I really do hope that negotiations will lead to an outcome that can be accepted by the British people as well as the European Union.”