By Jeremy Bowen
BBC Middle East Editor
Mr Miliband took the decision after an investigation by British Police
Britain's foreign secretary David Miliband has taken the decision to expel an Israeli diplomat after the UK's serious organised crime agency turned up evidence that Israel cloned British passports.
The Israeli diplomat is not the ambassador himself, but the expulsion sends a very strong signal to Israel of Britain's disapproval and anger.
The indications are that the person who will go will be the head of the London station of Mossad - Israel's secret intelligence service.
Diplomatic sources say Britain does not have evidence that Mossad murdered senior Hamas official Mahmoud al-Mabhouh in Dubai.
However, the accusation was made by police in the United Arab Emirates.
They presented CCTV footage showing an alleged Israeli hit squad, some disguised with wigs and others wearing tennis gear, following Mr al-Mabhouh in the hours before he was killed.
Britain's relations with Israel have been difficult for some time.
Mr Mabhouh was murdered in a Dubai hotel room, police say
Israel resents Britain's support for greater clarity in the labelling of products from Jewish settlements in the occupied Palestinian territories.
And late last year the former Israeli foreign minister, Tzipi Livni - now Israel's opposition leader - was forced to cancel a trip to Britain at short notice after a warrant was issued for her arrest on war crimes charges.
Worldwide, Israel is now under all-round diplomatic pressure from its allies.
The Americans, with the support of Britain among others, are pushing Israel to stop building for Jews on occupied land in Jerusalem, on the grounds that it makes negotiating peace with the Palestinians next to impossible.
If Israel is implicated in the murder of Mr al-Mabhouh, it won't be the first time.
During his first term as prime minister in 1997, Israel's prime minister Benjamin Netanyahu ordered the poisoning of another Hamas official, Khaled Meshaal in Jordan.
However the attempt was bungled after Mr Meshaal's bodyguard captured two of the Mossad hit team.
Mr Netanyahu was forced by a furious King Hussein to send the formula for the antidote to Jordan.
Mr Netanyahu also had to offer to release the Hamas leader Sheikh Ahmed Yassin to Jordan to mollify the King, who had recently signed a peace treaty with Israel.
Sheikh Yassin was a thorn in Israel's side until he was killed in an air strike in Gaza in 2004.
Mr Meshaal survived and is now the leading political figure in Hamas, living in exile in Damascus.
The attempt to kill him was one factor that led to the Israeli public turning against Mr Netanyahu in elections in 1999.