Boris's pledge for free travel in 'grey vote' battle with Ken

Mr Johnson and Ken Livingstone will go head-to-head for the first time in the election contest today, with polls saying it is on a knife edge. They will appear in front of 200 pensioners at hustings organised by charity Age UK London.

With 72 days until the election, both candidates made their bid to secure the all-important vote - an area where Mr Johnson has a massive lead.

At today's debate Mr Livingstone will pledge to help cut Londoners' energy bills by £150 a year if elected on May 3. Mr Johnson will say that every Londoner will be able to travel free on London's transport network after their 60th birthday.

Under the last Labour government the age for concessionary travel was linked to the rising state pension age for women. It has meant a gradual increase in the age Londoners are receiving the Freedom Pass and that will continue to go up under current rules to a maximum of 66.

The Government last year accelerated plans to increase the state pension age. Currently some Londoners are receiving their Freedom Pass aged 61.

"I said that Londoners over 60 would get the 24-hour Freedom Pass and I'm a man who keeps my promises," the Mayor said. "I'm conscious that my promise of free travel has been eroded by a decision from Ken Livingstone's Labour Party to raise the age where Londoners qualify for the Freedom Pass. So today I renew my pledge to elderly Londoners that they will get free travel from the age of 60."

More than 400,000 Londoners could benefit from the changes, sources close to Mr Johnson said. The pass is provided and mostly paid for by the 33 borough councils, but it is understood Mr Johnson will make up the financial shortfall, which would be around £8 million-£10million in the first year.

Meanwhile Mr Livingstone said he would cut the cost of living for Londoners through series of new measures to tackle rising energy bills. The Labour candidate said London has lost out on more than £400 million of funding for home energy efficiency schemes in recent years.

He said he would ensure London gets a fair share of the £1.3 billion per year that energy companies are required to spend on home insulation from 2013.

He also said he would prioritise insulating older people's homes and establish the first London Energy Purchasing Co-operative. This would cut the price Londoners pay for electricity and gas by purchasing energy on the wholesale markets, freeing London from major suppliers who have presided over huge price increases.