Andy Burnham was last night facing claims that he has breached Commons rules by not declaring hospitality worth thousands of pounds.
The Mail on Sunday can reveal the Prime Minister has not declared that he benefited from an exclusive VIP party in June last year as Mayor of Manchester.
The £6,600 party, given in his honour during a trip to Japan, was held exactly one year before Mr Burnham was re-elected as an MP.
But under strict Commons rules, MPs must disclose all relevant financial interests for the previous 12 months before they are elected.
Last night he was challenged to declare the interest immediately or be reported to the parliamentary standards commissioner.
Tory MP Charlie Dewhirst said: 'At a time when the declaration of gifts is under such a spotlight and after all of Keir Starmer's problems with freebies, it is surprising that the Prime Minister hasn't been more transparent.
He should declare this immediately and apologise for his carelessness. If not, then the parliamentary standards commissioner should investigate at once.'
Number 10 insisted last night that the reception had not been declared because the overall visit by the then Manchester mayor had started before the 12-month reporting period for newly-elected MPs.
Prime Minister Andy Burnham is facing pressure over claims he failed to declare a £6,600 VIP party held in his honor in Osaka, Japan, in June 2025 during his time as Mayor of Greater Manchester
Conservative MP Charlie Dewhirst (pictured) criticised the Prime Minister's actions
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A spokesman said: 'The PM went on this trip in his official capacity as Mayor of Greater Manchester. 'This was not registered as the trip began before the registrable period.'
However, the MoS understands that the PM's office will now check with the standards commissioner over whether the party should be declared.
Before he returned to the Commons in June, Mr Burnham earned the nickname 'Air Miles Andy' for his love of foreign trips as Mayor of Manchester.
In June 2025, he went on a trade mission to Japan, with his staff then boasting it was the 'largest-ever UK delegation' to the country. As part of the five-day trip, Mr Burnham was the guest of honour at an evening ballroom reception in Osaka, paid for by his Japanese city hosts.
However, no record of the hospitality currently appears in his MPs' declaration of interests.
Reform UK leader Nigel Farage is facing accusations that he has broken the same declaration rules by not disclosing a £5million donation received in the year before he became an MP although Mr Farage has denied any breach.
The row over the party in Japan comes at a time when MPs are under fire for taking £400,000 worth of gifts and hospitality so far this year, despite the outcry in 2024 over Sir Keir Starmer accepting football tickets and clothing.
The list of 'freebies' accepted included £1,400 for Wimbledon singles final seats, £3,400 for Brit Awards tickets and £1,800 for exclusive access to the Chelsea Flower Show.
Last night, TaxPayers' Alliance campaign director William Yarwood said: 'Taxpayers will be sickened to see MPs helping themselves to hundreds of thousands of pounds in freebies while households are squeezed by sky-high taxes.
'Concerts, race days, flower shows and corporate hospitality look far too much like the Westminster gravy train carrying on exactly as before.
'MPs should show some restraint, stop acting like lobbyists' VIP guests and focus on delivering value for the people paying their wages.'