Theresa May, pictured attending church with husband Philip today, is facing a tough battle against rebels in the Commons and Lords

Theresa May is facing a bitter fight for Brexit this week with up to 27 Tory MPs ready to back moves to water down the historic EU Bill.

Conservative rebels are said to be plotting with Labour, the SNP and Liberal Democrats to pass key amendments to the legislation in the Commons.

The scale of the opposition has emerged as the parliamentary battle over Brexit enters a new attritional phase.

MPs have tabled more than 140 pages of amendments to the Bill - which is just 137 words long. There will be a series of clashes in the Commons next week after the Speaker selects which changes will be voted on.

Dissenters are hoping they will be able to force the PM to seek early approval from parliament for any deal struck with the EU - raising the prospect that MPs could strike it down and send her back to renegotiate.

Former ministers Anna Soubry and Dominic Grieve are among those considering voting to modify the legislation - alongside Europhile Ken Clarke who was the lone Tory rebel at second reading.

Ms Soubry told BBC1's The Andrew Marr Show: 'The PM has been absolutely clear. If she gets a deal she will be back to the House of Commons - in fact both chambers - and there will be votes, and rightly so.

'But if there is no deal then the Government will determine what happens next. I think it should it come into Parliament. I don't know why people are so fearful of that.'

But pro-Leave Tories condemned the objections as a backdoor way of derailling Brexit.

Steve Baker claimed there were as many as 27 Tory MPs who could vote with the opposition.

'This is a time to unite behind a democratic result not plot to repudiate it. Any vote to amend this simple Bill is a vote against implementation of the referendum result,' the MP said.

That figure was dismissed as being far too high by the pro-Remain camp, but with a Government majority of just 16 in the Commons, the voting arithmetic may be tight.

There are also signs that Jeremy Corbyn will make another concession to his own pro-EU MPs by letting them abstain on the third reading of the Bill on Wednesday.

His allies believe the compromise could be the only way to stop the party's divisions becoming even more catastrophic.

The rearguard action against Brexit is likely to be even more fierce in the Lords, where the government does not have a majority and members are not answerable to voters.

Jeremy Corbyn was out and about at Finsbury Park Mosque to mark 'Visit My Mosque' day ahead of another tortuous week in parliament as the PM pushes through Brexit legislation

MPs overhwelmingly passed the EU Bill at second reading last week - but Europhiles are expected to try to water down the government's approach this week

A cross-party group of Europhiles calling themselves 'the Network' is said to be coordinating opposition to the government's plans in the upper chamber.

Former Lib Dem leader Paddy Ashdown and Labour peers Peter Hain are among those involved, according to the Sunday Times.

Among the amendments they will be seeking when the Bill comes to the Lords next week will be a clause giving parliament an early vote on whatever deal is struck with the EU.

Tory former minister Lady Altmann signalled she would consider backing changes to the draft law.

'I am very concerned about the implications for jobs and the corporate landscape if we have seriously abandoned the idea of being members of the single market and the customs union,' she told the newspaper.

Focal points for rebels include guarantees that EU nationals already living in Britain will be allowed to stay, and ensuring there is not a 'hard' border between Northern Ireland and the Republic.

The rearguard action against Brexit is likely to be most fierce in the Lords, where the government does not have a majority and members are not answerable to voters

Former chancellor Lord Lamont said Mrs May should call a general election if peers 'obstruct' the Brexit process.

'In the end the Lords normally defer to the Commons after asking it to think again, maybe once, maybe twice or more ... the scope for mischief is there,' he wrote in The Sun on Sunday.

'If the Lords and the Commons in league with each other were to obstruct and thus sabotage the Government's timetable, it is obvious what the PM should do.

'She should immediately call a General Election in which she makes it clear first that we are definitely leaving the European Union and second that the House of Lords would be abolished.

'I would be sorry to see it go. In many ways it does a fine job. But if it over-reaches itself, its days will deservedly be numbered.'