Sir Keir Starmer's top aide has been accused of 'subverting' Cabinet ministers in a bid to secure a bailout for the £310million rebuild of a derelict stadium in Belfast.
Sue Gray, the Prime Minister's chief of staff, is reported to have angered senior Government figures by 'personally dominating' negotiations over Casement Park.
The dilapidated sports ground has been earmarked to host five football matches at the 2028 European Championships, which is being hosted by the UK and Ireland.
But there are concerns the Belfast venue will miss out on staging games due to an ongoing row over the cost of refurbishment.
According to The Times, Ms Gray's close interest in the Casement Park project - in her native Northern Ireland - has caused resentment among Labour ministers.
Sue Gray, the Prime Minister's chief of staff, is reported to have angered senior Government figures by 'personally dominating' negotiations over Casement Park.
The dilapidated sports ground has been earmarked to host five football matches at the 2028 European Championships , which is being hosted by the UK and Ireland.
The dilapidated sports ground has been earmarked to host five football matches at the 2028 European Championships , which is being hosted by the UK and Ireland.
They have been told there is no money for new spending commitments as Chancellor Rachel Reeves keeps a tight rein on Whitehall budgets.
Ms Gray ran a pub near Newry, County Down, at the height of the Troubles and was the top official at Stormont's Department of Finance between 2018 and 2021.
A Stormont source familiar with discussions about a bailout for Casement Park described Ms Gray as 'very close' to Conor Murphy, the Sinn Fein finance minister.
Her involvement was also branded 'constitutionally improper' by a Whitehall source, who desribed it to the newspaper as 'an unelected member of staff spending public money on an area of interest to them, subverting Cabinet'.
It was reported that Ms Gray was pushing for the UK Government to announce new funding as early as this week.
But Downing Street sources said no decision on the future of Casement Park had been made and an announcement was not imminent.
They also said suggestions Ms Gray was 'personally dominating' negotiations were overblown.
The PM's official spokesman said: 'We all want to see great games of football played across the whole of UK and Ireland in 2028....these discussions remain ongoing.
'You would expect the PM's chief of staff to work on a broad range of areas.'
At present, there is insufficient funding available to pay for the rebuild of Casement Park, which would cost at least £200million and would have to be completed by mid-2027.
If the stadium isn't completed on time, UEFA would be forced to move the five fixtures to other host countries, leaving Northern Ireland without any games.
In February, the Irish government announced it is prepared to pay more than £40m to help the project. The Stormont executive has pledged £62.5m.
The GAA has pledged £15m but their new president Jarlath Burns said that is the limit.
Six of the 10 proposed Euro 2028 venues are in England - Wembley Stadium, the Tottenham Hotspur Stadium, Everton's new stadium at Bramley-Moore Dock, the City of Manchester (Etihad) Stadium, St James' Park in Newcastle and Villa Park in Birmingham.
The Millennium Stadium in Cardiff, Hampden Park in Glasgow and the Aviva Stadium in Dublin are the others.