Theresa May's personal ratings are the worst for any prime minister one month after a general election, Ipsos MORI said on Thursday 20 July.

The company's latest poll, of more than 1,000 people between 14 and 18 July, gave the Conservative premier a net satisfaction score of -25, with just one in three (34%) of respondents saying they are satisfied with her performance. This is down 22 points from April when the snap election was called.

Labour leader Jeremy Corbyn, in contrast, has seen his net satisfaction score rise to -1.

The left-winger is now more popular amongst his own party supporters than May is with hers. Ipsos MORI said three quarters (75%) of Labour supporters are satisfied with Corbyn, while one in five (19%) say they are dissatisfied.

This compares with two in three (66%) Conservative supporters who are satisfied with May and 27% who are dissatisfied.

"The turnaround in May's ratings is unprecedented in our previous data on Prime Ministers – from a historic high at the start of the campaign to a historic low just one month after an election, while also seeing her position among her own party supporters weakening and Jeremy Corbyn's campaign surge continuing," said Gideon Skinner, head of political research at Ipsos MORI. "Having said that, she still has the edge as most capable PM among over 35s."

But despite shifts in leadership satisfaction ratings, the research revealed that the British public still see May as being more capable at the job of prime minister. Just under half (46%) pick May, against 38% for Corbyn – little change from Ipsos MORI's June final election poll when 47% chose May and 36% Corbyn.

The pollsters' latest voting intention figures put Labour on 42%, the Conservatives on 41%, the Liberal Democrats on 9%, Ukip on 3% and the Greens on 2%. The findings comes as the Houses of Parliament break up for their summer recess.

May, who is going to northern Italy for her summer holiday, has been forced to warn her own cabinet ministers after a series of briefings against Chancellor Philip Hammond. "There is no such thing as an unsackable minister, but at the moment the team is together and we are getting on with the job of delivering what we need to do," she told LBC Radio.