So what's behind the crisis?
The key issue is there aren't enough drivers to supply petrol.
There's an estimated shortage of more than 100,000 HGV drivers and petrol is only the latest industry to be hit.
The lack of drivers has caused problems for a range of industries - from supermarkets to fast food chains.
Fuel tanker drivers need additional safety qualifications on top of their HGV licence to be able to transport chemicals such as petrol.
How did the petrol shortage start?
Late last week, Oil firm BP warned that it would have to "temporarily" close a handful of its petrol stations, because of a lack of lorry drivers. Long queues started to build up outside stations across Great Britain over the weekend, amid fears that petrol might run out.
Urban areas have been hardest hit, while Northern Ireland has been unaffected.
The panic buying was said to be caused by media reports of a leaked government briefing discussing the shortage of HGV drivers. Some analysts and politicians linked the driver shortage to Brexit, although transport secretary Grant Shapps denied this, whilst others blamed the COVID-19 pandemic.
What caused the driver shortage?
There are a number of reasons - and many countries across Europe have been affected - but the UK has been especially badly hit.
After Brexit, many European drivers returned to their home countries, or moved elsewhere, because working in the UK involved additional border bureaucracy which had an impact on their income. The pandemic saw even more drivers return to their home countries, with few coming back. Meanwhile, some older drivers have retired and there is a huge backlog in HGV driver tests due to Covid.
Has the petrol shortage improved?
The PRA - which represents nearly 5,500 of the UK's 8,000 filling stations - says that "trying to calm this down appears to be a monumental task at the moment". It says that more than a quarter (27%) of its members' petrol stations were out of fuel on Thursday, compared with two-thirds on Sunday.
On Wednesday, the Prime Minister Boris Johnson and Business Secretary Kwasi Kwarteng said there were signs that the petrol crisis was "stabilising" and urged people to buy petrol as they normally would.
There has been no improvement in petrol supplies at independent petrol stations since Wednesday, according to industry body the Petrol Retailers Association "There's been no easing off of the pressure from drivers wanting to refuel whenever they can, wherever they can, " said PRA chairman Brian Madderson.
The government had said it thought the situation was starting to get better.
What is the government currently doing?
The Ministry of Defence is preparing about 150 qualified military drivers to deliver fuel - and has another 150 personnel ready to support them. The Department for Business, Energy and Industrial Strategy (BEIS) says it will also draw on some of the reserve fleet of 80 tankers which the government keeps for emergencies.
Other measures include: A suspension of competition law between Oil firms, which the government said would make it easier for companies to share information about fuel supply, and prioritise areas most in need
An offer of temporary visas to 5,000 foreign fuel tanker and food lorry drivers (as well as 5,500 poultry workers) in the run-up to Christmas - although some business organisations, such as the British Chambers of Commerce have criticised this as "insufficient"
The process for getting an HGV driver licence will be sped up, and nearly one million letters have been sent to existing HGV drivers to encourage them back into the industry, plus there are plans to train 4,000 others
Can key workers get fuel?
The doctors' body the BMA, the teachers' union NASUWT and some politicians including London Mayor Sadiq Khan want key workers to be given priority access to petrol stations to avoid disruption to essential services.
However, the government hasn't announced plans to prioritise key workers as it did with nursery and school places during the pandemic.
Is there a limit on how much petrol I can buy?
The government has powers to limit how much fuel drivers can buy, and the hours when they can buy it, but there's no indication it plans to use them.
Some petrol stations have introduced a £30 cap on the amount of petrol people can buy.
However, the PRA said it didn't want garage staff to be put at risk "confronting" customers.
Is petrol in danger of running out?
No - Oil companies have stressed there is plenty of fuel available. They say that the shortage is being caused by "temporary spikes in customer demand" - or as PRA chairman Brian Madderson put it, "panic buying, pure and simple".
The government has claimed media coverage has inflamed the situation.
What's happening to fuel prices?
Petrol prices are at an eight-year high. The average petrol price at UK forecourts was 135.19p a litre on Monday, up from 134.86p a week earlier. The price of a litre of diesel rose from 137.35p to 137.95p over the same period. The RAC has said it's aware of a small number of retailers "hiking prices" in the current crisis.