LABOUR and the Lib Dems have called for an investigation into claims Liz Truss broke strict spending rules around a campaign event. 

The Foreign Secretary is under increasing pressure to answer questions over a “Fizz with Liz” champagne dinner held last October at an exclusive Mayfair club paid for by millionaire businessman Robin Birley.

According to the Independent, around 12 Tory MPs are said to have attended the function - reportedly worth £3,000.

Ms Truss, like all MPs, must declare any gifts to Parliament’s register of interests worth more than £300. That includes hospitality.

The dinner does not appear on the most up-to-date copy of the register. 

This morning, Labour said Ms Truss had also not declared the gathering in her capacity as a Minister under the Ministerial Code. 

Her spokesperson has previously claimed the dinner with “nothing to do” with Ms Truss and that she was one of a number of Conservative MP invited by “organiser and host” Mr Birley.

However, the Independent has obtained a copy of the invite which was sent from her Commons email address.

It said: “Liz Truss MP is delighted to invite you to attend a dinner at 5 Hertford Street on 26 October at 7.30pm. Most grateful if you could confirm attendance by 10 October. Best wishes, Office of Liz Truss.”

One MP who attended told the paper: “Liz was centre of attention, in great form and we discussed all sorts of things.

"We had champagne, cocktails, wine and a lovely three-course meal. Mr Birley turned up briefly to say hello.”

Another MP said: “Liz said it was time to stand up for Conservative values. She didn’t talk about the leadership but we all knew why we were there. She wanted our support.”

David Davis, who is supporting Rishi Sunak, told the paper: “We have just lost one prime minister after he broke the rules and couldn’t bring himself to tell the whole truth to the House of Commons.

"It would be a tragedy if a would-be prime minister did the same before they even got into Downing Street.”

Labour’s Deputy Leader Angela Rayner and Shadow Leader of the House Thangam Debbonaire have written to Simon Case, the Cabinet Secretary, calling for an investigation.

Their letter says that by using parliamentary paper and "explicitly inviting colleagues within her capacity as an MP via her parliamentary email address, Ms Truss’s event clearly falls under the transparency requirements of the Members Code of Conduct."

They added: “However, as Foreign Secretary, it is likely Conservative members attended this event in order to be in the company of the Foreign Secretary, and it would therefore be expected that she would make ministerial declarations in the usual way.

“There are serious questions for the Foreign Secretary to answer about why she failed to declare this large sum of hospitality funding, and why she now claims she had ‘nothing to do’ with the event’s organisation, despite sending out personal invitations to all attendees.”

They added: “We ask that you do the necessary investigation into the numerous questions raised by these allegations. The public has a right to know why such a significant donation for hospitality was not properly declared by the Foreign Secretary.”

Ms Rayner said: “Liz Truss is corked from the same vintage as Boris Johnson. She thinks the rules don’t apply to her and she can take the British public for fools.

“There must be an urgent investigation into the murky donations made by this millionaire aristocrat and why as Foreign Secretary, she has failed to come clean about them."

Meanwhile, the Lib Dems have called on the Commons standards watchdog to investigate. The party's deputy leader, Daisy Cooper said: “The last thing this country needs is another Boris Johnson. Yet here we are again, this time hearing allegations of rule-breaking levelled at the Conservatives’ frontrunner for prime minister. You’d be forgiven for feeling a sense of deja vu.”

Ms Cooper added: “Liz Truss must come clean and explain who paid for what at her schmoozing events. I hope the Parliamentary Commissioner for Standards will get to the bottom of it before public trust is damaged any further.”

A spokesman for Ms Truss told the Independent: “It was not organised for her, on her behalf or by her.

“She was invited by Robin Birley with loads of MPs. It was put on by Mr Birley to discuss low tax and deregulation.”

The paper said it then asked for an explanation about the email. Ms Truss’s spokesman replied: “I am aware of the email but it was not her event. We are sticking with the line.

“We have had very clear advice. A declaration would only need to be made if there was a benefit to Liz, or it was above the threshold for individual declarations for MPs’ register of interests.

“Liz was one of a number of MPs in attendance.”