Work and pensions secretary Esther McVey has been forced to apologise after being criticised by the national audit watchdog for making “incorrect” claims about Universal Credit in Parliament.

In an open letter to the minister from the National Audit Office (NAO), auditor general Sir Amyas Morse said parts of Ms McVey’s statement on Universal Credit were incorrect and unproven.

Sir Amyas said it was “odd” McVey had told the Commons that the NAO did not take into account recent changes in the administration of Universal Credit, when the report was “fully agreed” with senior officials at her department days earlier.

Sir Amyas also took issue with McVey’s assurance that universal credit was working, describing the claim as “not proven”.

Addressing the Commons following the publication of the letter, Ms McVey said: “While speaking in Parliament in answer to questions on the NAO report into Universal Credit, I mistakenly said that the NAO had asked for the roll-out of Universal Credit to continue at a faster rate and to be speeded up.

“In fact the NAO did not say that and I want to apologise to you and the House for inadvertently misleading you.”

She added: “What I meant to say was that the NAO had said that there was no practical alternative to continuing with Universal Credit.”

Margaret Greenwood, Labour’s shadow work and pensions secretary, earlier said McVey should apologise or consider her position.

She said: “This is a very serious matter. Esther McVey appears to have misled Parliament in misrepresenting the findings of the NAO report.

“She sought to rubbish the NAO report, rather than respond to its findings, which were damning of her government’s flagship social security policy, even though her own department had agreed the report prior to its publication.”

SNP social justice spokesperson, Neil Gray MP, said the apology did not go far enough and urged Esther McVey to return to the Commons immediately to provide a statement on Universal Credit.

Mr Gray said: “The government has been happy to mislead not just the Commons, but the public about Universal Credit for years, now they’ve been found out.

“All of Esther McVey’s lines in defence of Universal Credit have been torpedoed by the National Audit Office, which is why she was so desperate to undermine them on Monday. We knew she was wrong then, but her partial apology is just not enough and poses more questions than answers.

“Esther McVey needs to come back to the House immediately and give a statement on Universal Credit, this time advising how she will address the concerns of the NAO, why she lied to the House and why she appears at odds with her own DWP officials.”