Roads surrounding Leicester's New Walk Centre could be partially shut for up to five months when the two towers are demolished, an expert has said.

City mayor Sir Peter Soulsby announced this week that the council's headquarters would be brought down and rebuilt within two years.

William Eyre, owner of Lost World Demolition, said the task could cost around £2 million.

He said: "It's a concrete building which was constructed in the 1960s, so the asbestos content means it will be expensive to demolish. Extra care will have to be taken to control the dust.

"They'll start the demolition by fencing off and securing the site. Then the building will have to be soft stripped, which means the interior will be stripped of things such as door frames and other fixtures and fittings.

"By this stage, the lifts will have been removed so lots of this material will be put down the lift shaft to be removed from the site.

"After that, it's a case of removing the building floor by floor, from the top down.

"Because it's in a built-up area it's likely the roads and pavements close to the site will have to be closed – and the whole job is likely to take around 20 weeks."

Mr Eyre, from Leicester, who pulled down the Richard Roberts factory, the Byfords factory, part of Charles Street police station and part of the Towers Hospital, in Gypsy Lane, said the cost of the demolition would be at least £1 million, but could be double that depending on the amount of asbestos in the two buildings.

Earlier this week, Sir Peter said the tower blocks would have to come down, due to engineers' fears they are unsafe.

He said rather than moving staff to existing buildings in the city, he would prefer to see a new headquarters built on the same site. The project will cost tens of millions of pounds.

He had originally preferred the idea of relocating staff within the city, but the council says there is not enough space.

A council spokesman said: "There are about 1,200 staff currently at New Walk Centre, which is about two-thirds of its capacity, with a number of staff already having been moved out to reduce the stress on key areas of the building. The other city council-owned buildings are already occupied close to their maximum capacity.

"Even taking into account predicted job losses and redundancies over the coming years, there will still be about 2,450 staff working in council-owned city centre buildings, which need about 20,830 square metres of space.

"Without New Walk Centre, we are left with only about 14,300 square metres of office space, meaning we are short by 6,600 square metres."