Firefighters used the relative calm over the weekend to establish containment lines around the Lithgow fire that is blazing on a 200km front and has already burnt 38,000 hectares of bushland.

Emergency services and nearby mines and residents are bracing themselves for worsening conditions this week as north-westerly winds are expected and hot dry conditions prevail.

NSW Premier Barry O’Farrell has called a state of emergency to enable the Rural Fire Service to take pre-emptive action to save lives and property as fire commissioner Shane Fitzimmons warns that the fires are the worst experienced in the state since 1968.

“They have the very real potential to go right out to the eastern end of the Hawkesbury, right down into the northwest area of Sydney including Richmond,” he said.

“That's what we are talking about, the run from Bilpin right through to Richmond.

“We are also talking about the fires coming down the northern areas of the Great Western Highway, everywhere from Blackheath to Katoomba, Leura and all the townships all the way along to places like Springwood and Winmalee.

“That's the magnitude. I sincerely hope it's not realised and we end up somewhere in between but what we can't ignore is the probability, based on the weather forecast and based on the current fire behaviour that we've experienced and which we are continuing to experience across these fire grounds.”

The access corridors to mines around Lithgow have been blocked by the bushfires that have swept through the upper Blue Mountains with the Bells Line of Road closed and the nearby town of Bilpin being evacuated.

The loss in production through the disruption caused by the bushfires is too early to calculate with transport of staff, contractors and machinery all being affected.

Around the state, emergency services have been stretched attempting to control fires in the lower Blue Mountains, the Southern Highlands, the Central Coast, the Hunter Valley, Newcastle, Lake Macquarie and the Illawarra.