The Conservatives have lost their lead in two opinion polls.
The drop comes as the sleaze scandal continues to engulf the party and House of Commons.
One poll carried out for the Daily Mail has Labour six points ahead.
Another for The Times has the Tories level with Labour.
The YouGov survey for the Times found that 60% of those asked agreed with the statement “the Conservatives these days give the impression of being very sleazy and disreputable”, up from 51% in April.
Only 33% agreed with the same statement for Labour.
The Savanta ComRes poll for the Daily Mail said Labour now held a six-point lead over the Conservatives, reversing a three-point Conservative lead last week.
The Conservatives have been in power since 2010.
It has rarely not topped opinion polls during that time.