The Mayor of London Boris Johnson and union leader Bob Crow went head-to-head in a heated exchange on LBC Radio ahead of the London Underground strikes.

The war of words ensued hours before members of the Rail, Maritime and Transport Workers Union (RMT) and the Transport Salaried Staffs Association are due to walk out for 48 hours from 9.30pm on (Tuesday) 4 February and again a week later in a row over job losses.

Crow, the general secretary of the RMT, called into Johnson's weekly phone-in segment, Ask Boris, on LBC Radio.

The union leader called on the Mayor of London to suspend the planned ticket office staff cuts across the underground network and said his members would suspend their industrial action if he made the move.

But Johnson bit-back and claimed there was "absolutely no need" to go ahead with the strike.

"Yes, of course, there are job losses involved in what we are proposing." Johnson stressed.

"We accept that. But there are no compulsory redundancies.

"[But] we've already had more than 1,000 people show an expression of interest in voluntary redundancies."

Crow dismissed Johnson and compared the "ultimatum" to being like "Henry Ford saying you can have any colour car you want as long as it's black".

But Johnson replied by claiming ticket offices were "old technology" and he urged Crow to call off the "pointless" strike.

Crow hit back at Johnson by explaining that the Conservative politician had campaigned on not closing the London Underground's ticket offices in his battle to become Mayor of London.

However, Johnson said that was "six or seven years ago" and "massive improvements" in technology has meant fewer and fewer people use the offices.

London Underground has said it will enlist volunteers to help run the tube network throughout the industrial action.

"Our customers and staff are at the very centre of our plans for London Underground," said Mike Brown, London Underground managing director.

"All Tube stations will remain staffed and controlled at all times when services are operating, and we'll be introducing a 24-hour service at weekends during 2015.

"In future, there will be more staff in ticket halls and on platforms to help customers buy the right ticket, plan their journeys and to keep them safe and secure.

"We're committed to implement these changes without compulsory redundancies and there'll be a job for everyone at LU who wants to work for us and be flexible."