LONDON, Jan 8 (Reuters) - Britain"s government will seek an extra 4 billion pounds ($5.4 billion) from property developers to fund repairs to dangerous apartment blocks, in the wake of a fire that killed more than 70 people in 2017, the BBC reported. The deadly blaze at Grenfell Tower, a 23-storey social housing block in west London, revealed the widespread use of flammable cladding on apartment blocks across the country, requiring expensive removal or round-the-clock fire watches. The government has committed around 5 billion pounds for repairs so far, and last year imposed a levy on housebuilders to raise 2 billion pounds towards the cost over the next 10 years. The BBC published government correspondence late on Friday showing that ministers would seek a further 4 billion pounds from developers to fund repairs to a wider range of apartment blocks and reduce costs for the apartments" leaseholders. "You may use a high-level "threat" of tax or legal solutions in discussions with developers as a means to obtaining voluntary contributions from them," Simon Clarke, chief secretary to the Treasury, wrote to Michael Gove, secretary of state for housing. The money would be used to provide government grants to fund repairs for blocks with a height of at least 11 metres (36 ft). Previously only government loans had been available for blocks that were less than 18.5 metres high. However, Clarke told Gove that if the property developers would not pay up, he would have to find the money from the existing housing budget. A spokesperson for the Department for Levelling Up, Housing and Communities had no immediate comment. Legal liability for the repairs is disputed, and in practice the leaseholders of individual apartments have often faced bills for tens of thousands of pounds each for repairs from the owners of the apartment blocks. Developers who have had to pay out to replace cladding include Barratt (BDEV.L) and Persimmon (PSN.L). ($1 = 0.7361 pounds)