Theresa May will place a triple lock on Brexit in the Tory manifesto to stop obstruction by diehard Remainers.

Tory sources say she is set to include specific pledges to overcome opposition within her party and in the Lords.

The manifesto is expected to commit the Conservatives to ending EU free movement and pulling out of both the single market and European Court of Justice.

Senior Tories see the three measures as essential in delivering last year's referendum result.

Theresa May (pictured) will place a triple lock on Brexit in the Tory manifesto to stop obstruction by diehard Remainers

Mrs May took her campaign straight to the battleground of Bolton last night, delivering her stump speech for the first time and greeting supporters

The rally came after the penultimate Commons clash between Mrs May and Labour leader Jeremy Corbyn before the election, pictured

One insider said Tory Remainers would be required to sign up to the package, 'locking them in'.

Including the pledges in the manifesto will also make it much harder for peers to block Brexit.

Mrs May is expected to use the manifesto to ditch a number of high-profile policies from the Cameron era. Yesterday she left the door open to watering down – or even scrapping – Mr Cameron's flagship vow to spend 0.7 per cent of national income on foreign aid.

Ministers refused to say whether the costly 'triple lock' on pensions will be retained, or whether the pledge to reduce net migration to the 'tens of thousands' will be kept when the manifesto is published in a fortnight. The move came as:

MPs voted by 522 votes to 13 to back a snap election on June 8;

Mrs May kicked off her campaign with a warning of a 'coalition of chaos' led by Jeremy Corbyn, Nicola Sturgeon and Tim Farron;

Downing Street moved to calm the row over Mrs May's refusal to participate in TV debates with Jeremy Corbyn;

Labour threatened to hit 1.6million higher earners with higher taxes;

George Osborne finally bowed to pressure to quit parliament;

Commons Speaker John Bercow said he would stand for another term;

Gisela Stuart, a prominent Leaver, led an exodus of Labour MPs choosing to quit rather than campaign for Mr Corbyn.

Setting out her 'Brexit prospectus', Mrs May said: 'When people voted to leave the EU they did vote to end free movement as it has been – they voted for us to have control of our laws so we are not subject to the ECJ.

'We will be ensuring we negotiate the best possible deal with the EU – a deal which will cover the various issues that people are really concerned about in terms of ensuring control of our borders, control of our laws, control of our money.'

A Tory source said: 'All Conservative candidates will have to stand on the manifesto – it will lock them in and provide a much stronger mandate. It will also send a message to the House of Lords that they cannot get in the way.'

Under the so-called 'Salisbury convention', the upper house cannot block legislation enacting pledges made in the manifesto of the governing party, although it can delay it for a year. Tory grandee Sir Desmond Swayne yesterday said senior peers, including former cabinet secretary Lord Butler and leading human rights lawyer Lord Lester, had told him 'we would not leave the European Union because they were in a position to prevent it and would do so'.

He added: 'The policy the Prime Minister announced, of pursuing a general election and securing a mandate in this house and a mandate to bind the other place to the Salisbury convention, is therefore essential.'

Dominic Raab, a former Tory justice minister, also welcomed the plan, saying: 'It is a sensible move, which is consistent with the pledges the PM has made.

Mrs May (pictured leaving No 10 today) is set to use the manifesto to ditch a number of policies which were introduced when David Cameron was in charge

The manifesto is expected to commit the Conservatives to ending EU free movement and pulling out of both the single market (pictured, the European Parliament)

'It's important to make sure we get the strongest possible mandate to deliver the best deal with our European friends.

'It will also give us a clarity of position which should be respected across both houses of parliament.'

The move will leave prominent Tory Remainers, such as Nicky Morgan, Anna Soubry and Kenneth Clarke in a potentially awkward position.

Miss Soubry yesterday insisted that a bigger Commons majority would make it easier for the Prime Minister to face down Tory Brexiteers and compromise with Brussels. She said: 'A bigger majority will enable the PM to see off the Hard Brexiteers. She is clear – she wants a deal.'

But she and others could now find themselves having to sign up to a manifesto incorporating key elements of so-called 'hard Brexit'.

Speaking at an election rally in Bolton last night, Mrs May said: 'Give me the mandate to fight for Britain and give me the mandate to deliver for Britain.'

Senior Tories see the three measures as essential in delivering last year's referendum result which saw the UK vote to leave the EU (pictured, the European Parliament)

Mr Corbyn, who will launch his campaign today, dismissed Mrs May's argument that she needs a fresh mandate to deliver Brexit, and taunted her over her refusal to agree to a live TV debate.

In her statement announcing her plan for a snap election on Tuesday, Mrs May said Britain would go to the polls on June 8 specifically to strengthen her mandate to deliver the result of last year's historic EU referendum.

She singled out opposition to Brexit from Labour, the Liberal Democrats, the SNP and the 'unelected' House of Lords as her reason for going to the polls.

Bonfire of the chumocracy's legacy: Cameron's cherished aid target set to be ditched by May so she can spend billions more on the Armed Forces

Theresa May is considering ditching David Cameron's foreign aid target – and pouring billions more into the armed forces.

Aid is one of a series of Cameron-era pledges that could either be abandoned or significantly adjusted in the Tory manifesto.

Downing Street is also reviewing the pledges to cut net migration to the 'tens of thousands' and to maintain the pensions 'triple lock'.

Mrs May yesterday refused to endorse the commitment to spend 0.7 per cent of national income on aid every year. It was put into law by Mr Cameron and Nick Clegg but has been blamed for leading to hugely wasteful expenditure.

And last night she cancelled an appearance with Microsoft founder Bill Gates – a leading advocate of the 0.7pc target who hours earlier had called for the pledge to be kept.

Theresa May is considering ditching David Cameron's foreign aid target – and pouring billions more into the armed forces

In the Commons, the Prime Minister was asked explicitly whether she backed both the aid target and the Nato goal of spending 2 per cent of GDP on defence.

She endorsed maintaining defence spending but pointedly refused to back the aid target – prompting speculation it will be ditched. With international agreement, money spent on military action to help support fragile states in Africa and elsewhere could also be counted as aid.

Such a move would be resisted by International Development Secretary Priti Patel, who says the pledge is key to the Government's 'Global Britain' brand post-Brexit. The aid pledge could also be adjusted.

Another less radical option would be to allow aid to be 'smoothed out' over a parliament, giving ministers more discretion about when to spend the money. But this would mean the budget would carry on rising in line with national income.

There are growing calls among Tory MPs for the aid target to be abandoned. The hugely expensive pledge to increase pensions every year by a set amount – the so-called triple lock – is also likely to be adjusted. It means the state pension must rise by the highest out of earnings, inflation or 2.5 per cent.

Work and Pensions Secretary Damian Green has hinted that increasing state pension payments so sharply is unsustainable.

There was also speculation that Mrs May could drop, or amend, the pledge to reduce net migration to the 'tens of thousands' in the manifesto. In a BBC interview, the PM was asked to endorse the pledge to bring net annual inflows to under 100,000, which has been Tory policy since 2009.

Aid is one of a series of Cameron-era pledges that could either be abandoned or significantly adjusted in the Tory manifesto

She instead said she wanted migration to be at 'sustainable levels'. But she reinforced her determination to cut numbers – stressing she had spent six years as Home Secretary fighting to reduce them.

Leaving the EU will mean the end of free movement, handing government full control over migrant numbers from inside the bloc. Net migration currently stands at 273,000 and has not been below 100,000 since the mid-1990s.

At Prime Minister's Questions, Tory backbencher Richard Benyon asked Mrs May to commit to both the Nato and aid targets, saying he was proud of the Government's record on both.

But Mrs May endorsed only the Nato pledge. 'We have committed to meet our Nato pledge of 2 per cent of GDP being spent on defence every year of this decade,' she said.

'We are delivering on that. We have got a £36billion defence budget that will rise to almost £40billion by 2020-21 – the biggest in Europe and second largest in Nato.'

On aid, she said the ministers 'are meeting our UN commitment'.

She added: 'I can assure him that we remain committed, as a Conservative party, to ensuring the defence and security of this country and to working for a stronger world.'

Tory MP Jacob Rees-Mogg said: 'We need to spend the amount we need to spend rather than setting targets. The 0.7 per cent target was always arbitrary. We need an aid budget for emergency support, but the rest should be charity or private investment.

The aid target – and a promise to put it in to law – was included in the 2010 Tory manifesto as part of Mr Cameron's attempts to 'detoxify' the party. Also a Lib Dem commitment, it became law in March 2015.