New discussions between union officials and Deputy Prime Minister John Prescott in the firefighters' pay dispute have been described by both sides as "constructive".

Fire Brigades Union (FBU) leader Andy Gilchrist met Mr Prescott today at the start of what the union had described as a "critical" 48 hours of talks to avoid another strike.

If this week's negotiations fail, the firefighters plan to walk out on Friday for eight days.

After the first meeting, Mr Gilchrist said further discussions would now have to be held.

But the prime minister's official spokesman said later there had still been no agreement reached on safety and how the FBU would respond to major incidents if it continued its strike action.

The first 48-hour strike ended last Friday with union leaders hinting that a compromise could be reached over their £30,000 pay claim.

Today, Tony Blair insisted that any rise would have to be linked to reform.

"One thing has got to be very, very clear - we cannot pay more money out unless it is tied to changes within the fire service," he said on ITV1's Tonight with Trevor McDonald.

Meanwhile, Chancellor Gordon Brown attacked the firefighters' pay claim.

He said it was "the wrong time, exactly the wrong claim, pursuing the wrong methods to demand wage rises so much higher than inflation".

Ahead of the latest talks, the government denied claims it refused to fund an offer of 16.1% over two years last summer which would have meant £25,000 a year.

The employers and the government say their position remains the same - any pay increase must be linked to modernisation.

The FBU executive was meeting later on Monday and could decide to reopen negotiations with local authority employers.

At the weekend Mr Prescott spent a few hours at his local fire station in Hull where firefighters claim he told them that he was in charge of cutting a deal.