The Armed Forces have begun helping to deliver fuel to petrol stations this morning (Oct 4) as London and the South East continue to struggle with shortages.
About 200 military personnel - half of them drivers - are being deployed as part of Operation Escalin in an effort to increase the number of tanker drivers.
Most of the troops, who have been on standby since last week, are working in London and the South East, where the worst shortages remain.
Photographs this morning showed personnel - believed to be airmen - arriving at the Buncefield Oil Depot in Hemel Hempstead, Hertfordshire, to help with the deliveries.
Many of them have been training with petroleum logistics company Hoyer in Thurrock, Essex.
Ministers have faced criticism for not sending them out earlier after a wave of panic-buying - prompted by reports that supplies to filling stations were being hit - led to chaos on the forecourts.
A government spokesman said:
"We are working closely with industry to help increase fuel stocks and there are signs of improvement in average forecourt stocks across the UK with demand continuing to stabilise.
"Stocks in London and the south of England have been recovering at slightly slower rates than other parts of the UK, so we have begun deploying military personnel to boost supply in these areas.
"More than half of those who have completed training to make fuel deliveries are being deployed to terminals serving London and the southeast of England, demonstrating that the sector is allocating drivers to areas most affected in this first phase from Monday."
While London and the South East remain hardest hit, the Petrol Retailers Association said problems were "virtually at an end" in Scotland, the North and the Midlands, where only 6% of filling stations were empty on Sunday.
In London and the South East, 22% of filling stations were dry, and 60% had both grades of fuel available.
Overall, 17% of petrol stations were empty in the UK on Sunday, while 67% had both grades of fuel available, the group said.
Operation Escalin was originally drawn up in preparation for possible fuel shortages following Britain's final withdrawal from the EU single market at the start of the year.
The Petrol Retailers Association (PRA) welcomed the military deployment but suggested it would have only a limited impact.
Gordon Balmer, its executive director, told Sky News that out of 1,100 sites it spoke to, some have been empty for over a week.
He added that the "pinch point" of the problem is in the South East and that it may take up to 10 days for some areas to build supply back to normal levels.
Mr Balmer also said there "may be a good chance" shortages could last up until Christmas if "drivers can't get through to solve the problem".
MP Penny Mordaunt said she had been in touch with fuel outlets in Portsmouth that have had no deliveries for nearly a week.
She tweeted:
"Surveyed forecourts last night and been directly in touch with managers in Portsmouth this morning.
"Still stations that have had no deliveries and have been completely out of both petrol and diesel for nearly a week."
Meanwhile, Prime Minister Boris Johnson said on Sunday that the crisis was "abating" and the military was being deployed as a "precaution".
But he has repeatedly refused to rule out shortages extending to the wider economy ahead of Christmas.
It is estimated that the UK needs at least 100,000 more HGV drivers to ensure supplies, and some businesses have warned that shop shelves could be empty if this is not addressed.
Mr Johnson has not ruled out a further relaxation of immigration rules to help ease the supply shortages - but he also insisted that he does not want to see a return to "a lot of low-wage immigration".
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The government has said 300 fuel tanker drivers will be able to come to the UK from overseas "immediately" under a bespoke visa which will last until March.
Some 4,700 other visas intended for foreign food haulage drivers will be extended beyond the three months initially announced and will last from late October to the end of February.
There have also been calls for the visa programme to be extended to HGV drivers in all sectors of the retail industry.
Elsewhere, Chancellor Rishi Sunak denied there was an "upside to people struggling with supply chain challenges" after Tory MP Chris Loder reportedly said shortages are in the "long-term interest" of the British economy.
He told Sky News:
"I don't think anyone would say there's an upside to people struggling with supply chain challenges and not being able to get what they want at the time they want it. No one wants to see that.
"What we've said more broadly is over time one of our desires is to transition ourselves to a higher wage, high skill economy, more productive economy."