SAUDI ARABIA is threatening to suspend diplomatic ties with Britain unless Downing Street intervenes to block an investigation into a 60m “slush fund” allegedly set up for some members of its royal family.

A senior Saudi diplomat in London has delivered an ultimatum to Tony Blair that unless the inquiry into an allegedly corrupt defence deal is dropped, diplomatic links between Britain and Saudi Arabia will be severed, a defence source has disclosed.

The Saudis, key allies in the Middle East, have also threatened to cut intelligence co-operation with Britain over Al-Qaeda.

They have repeated their threat that they will terminate payments on a defence contract that could be worth 40 billion and safeguard at least 10,000 British jobs.

The Saudis are furious about the criminal investigation by the Serious Fraud Office (SFO) into allegations that BAE Systems, Britain’s biggest defence company, set up the “slush fund” to support the extravagant lifestyle of members of the Saudi royal family.