Armed forces teams covering for striking firefighters will be ordered to cross picket lines to get access to modern equipment if public safety is at risk, the government has said.

The toughening stance of ministers came as firefighters were standing firm more than half way through their 48-hour walk out.

Fireworks exploded from a blaze in Manchester

As it emerged soldiers were already training to use modern appliances, Home Office Minister Lord Falconer said: "If public safety ultimately requires that the army cross picket lines to get the red fire engines then that is what will have to be done."

Earlier on Thursday the leader of the Fire Brigades Union, Andy Gilchrist, paid tribute to members who have crossed their own picket lines to answer emergency calls - but he again rejected the pay offer currently on the table.

The toughest test yet faced by troops manning the vintage Green Goddess fire engines came in Manchester when a huge fire broke out at a fireworks factory in the city centre.

Amid dramatic scenes, striking firefighters at a nearby station raised the alarm before temporarily crossing their picket line to help get a man out of the building.

They left the scene when troops arrived, and by evening the fire was out.

With concern growing at the ability of the stand-in firefighters to tackle such incidents with their elderly appliances, Lord Falconer said on BBC One's Question Time: "Ultimately public safety comes before picket lines."

If there were further eight day stoppages in addition to the one planned for next week, "it may well be necessary to think about which picket lines need to be crossed," he added.

Armed forces have not had to cross picket lines yet

Earlier, Downing Street confirmed some army units around the country had already begun training on spare appliances normally kept at the National Fire Training College.

In a further hint that troops could be ordered to cross picket lines, Deputy Prime Minister John Prescott insisted "all options are under review", pledging the government would "do what we have to do" to protect the public.

He kept up his criticism of the FBU, saying the strike was "wrong and unjustified".

And Mr Prescott also admitted that banning firefighter strikes was under consideration.

John Monks, the TUC general secretary, has warned that allowing the army to cross picket lines could have a harmful effect on relations between the government and the Fire Brigades' Union.

'War of attrition'

"At the end of the day, the government has got a duty to the public for their safety," he told BBC Radio 4's Today programme.

"But that [crossing picket lines] would be a signal to the FBU that this would be a long war of attrition and that will have a deleterious effect on what is happening.

"It will put even more strain on the kind of co-operation that has been shown by the FBU over night in the tragedies that have taken place and which we are all desperate about."

Meanwhile, a member of the Retained Firefighters' Union, which represents part-timers not on strike, said some managers are deliberately not calling them out to avoid causing friction with members of the FBU.

The man, who wanted to remain nameless, said: "To me, public safety is paramount and the feelings of a few individuals do not count."

But FBU leader Andy Gilchrist dismissed the claim as "nonsense".

He said his union was prepared to consider any "serious and significant" pay offer.

But he described the current offer from employers - amounting to 11% split over two years instead of the 40% they are demanding - as "insulting".

Army helped

Speaking at a rally in Edinburgh, he said the strike was "100% solid".

And at a rally in Belfast, he "applauded" firefighters who had helped army crews when lives had been in danger.

Since the strike began seven people have died in fire-related incidents, and another in a vehicle collision near Teesside Airport attended by the airport fire crew.

Other incidents across the country have included:

• In Birmingham city centre firefighters crossed their own picket line to help a man who was lying bleeding on the pavement after being stabbed in the head
• Green Goddess crews and retained firefighters tackling a large fire at a carpet warehouse in Rugby, in connection with which police arrested two teenage boys
• Striking firemen leaving their picket line in Caernarfon to help search for a child who had reportedly fallen into a river.
• Major disruption to London Underground services, when about 100 Tube drivers refused to work and 22 stations were closed for safety reasons
• Two police officers saving an unconscious woman, in her 20s, from a blazing flat in Essex, before a Green Goddess arrived
• Firefighters breaking a picket line to help rescue a motorist in Leeds trapped for an hour
• Firefighters in Londonderry leaving their picket to help five people injured in a head-on collision yards from the station.

Responses to incidents during the strike have been hampered by hundreds of hoax calls, which police have promised to trace.