"The government has today taken action to freeze the assets of Colonel Muammar Abu Minyar al-Qadhafi (Gaddafi), members of his family and those acting on their behalf or at their direction," the statement said.
Britain understands that Gaddafi owns around £20bn ($32.2bn) in liquid assets, mostly in London, according to the Telegraph newspaper.
"I have today taken action to freeze the assets...so that they cannot be used against the interests of the Libyan people," British finance minister George Osborne said in the statement.
"This follows the UN Security Council Resolution tabled by the UK and France," Osborne continued. "I decided to implement this UN resolution in the UK as quickly as possible, before the financial markets reopened.
"This is a strong message for the Libyan regime that violence against its own people is not acceptable," Osborne added.
British Prime Minister David Cameron later Sunday promised Gaddafi that he would use all the powers at his disposal to try to force the Libyan leader from power, telling him it was "time to go".
"We are now putting serious pressure on this regime," Cameron said. "The travel ban and the asset freeze are the measures we are taking against the regime to show just how isolated they are.
"There is no future for Libya that includes him," Cameron warned.
The Foreign Office statement warned financial institutions that the treasury would monitor compliance "rigorously".
According to reports, Gaddafi's British assets include bank accounts, commercial property and a £10m London home.
Britain's Department for Business, Innovation and Skills also signed an order to prohibit the export of uncirculated Libyan banknotes without a licence from the UK.
The British action follows that taken by Washington, which signed an order freezing the Libyan leader's US assets earlier Sunday.
Saturday, the UN Security Council unanimously ordered a travel and assets ban on Gaddafi's regime and a crimes against humanity investigation into the bloodshed blamed on the Libyan strongman.
It also called for an immediate arms embargo against Libya, where the UN says more than 1 000 people have been killed in attacks blamed on Gaddafi loyalists.
In line with the UN announcement, the government confirmed that it had revoked "existing export licences for goods and technology that could be used for internal repression."
"Export licences for military or paramilitary equipment to Libya will not be issued unless they fit within one of the exceptions set out in the (UN) embargo," the FCO statement added.