Support for the Conservative and Labour parties is neck and neck, according to new research.
A poll by market research company Opinium suggested the Tories have lost their seven-point lead from a fortnight ago, while Jeremy Corbyn's opposition has gained three points.
The survey of more than 2,000 adults in the UK also found an increase in approval of Mr Corbyn's Brexit response.
And 48 per cent of those surveyed believed Theresa May's deal was bad - up by three per cent from two weeks ago.
In a further blow to the Prime Minister, outright opposition to the deal from people who voted for her party in 2017 has increased from 19 per cent at the beginning of February to 24 per cent.
The research suggested the public was becoming disillusioned with the two parties, with 41 per cent thinking Labour and the Tories have become "extreme".
Two fifths (40 per cent) said a new political party would be the best way for them to be represented.
Adam Drummond, head of political polling at Opinium, said: "In recent weeks we saw the Conservatives taking a clear lead in the polls, partially in response to some of the first good news the Government has had in months.
"However, with every step forwards, there always appears to be another one backwards. The public are frequently reminded that delivering Brexit is a slow and laborious process, and the lack of progress since the last successful vote appears to have dampened the Conservative's lead amongst Leavers.
"A breakthrough in the polls won't be possible until a decisive change happens on Brexit."
Reporting by Press Assocation.
