Boris Johnson has called for Theresa May to take a Thatcher-esque attitude towards the proposed 'divorce bill' from the European Union.
For several months, reports have been circulating that the UK will be asked to pay the EU a fee of around £50bn as a price for leaving the union.
It's an idea which has gained momentum among some EU leaders. One of them, Irish Taoiseach Enda Kenny, told reporters at an EU summit in Brussels on Thursday the UK's contract with the EU had to be honoured.
He said: "When you sign a contract, you're committed to participate."
The Prime Minister's office has not ruled out the possibility of paying the bill or continuing to send the EU money for joint projects, but the Foreign Secretary has called for Mrs. May to stand resolutely against it.
He told reporters there was an "illustrious precedent" for this - the summit at Fontainebleau in 1984 where Margaret Thatcher demanded money back from the European Economic Community as the EU was known then, and obtained a rebate for the UK.
If applicable, the 'divorce bill' could become another battle for Theresa May in the Brexit negotiations, along with a fine of potentially up to £1.7 billion from the Office Européen de Lutte Antifraude for supposedly allowing illegal Chinese exports to flood intoEuropean markets.