Jaguar Land Rover's dealers and suppliers fear the British carmaker's operations will take another few months to normalise after a cyber attack that experts estimate could wipe more than £3.5bn off its revenue.

JLR, which is owned by India's Tata Motors, had been forced to shut down its systems and halt production across its UK factories since August 31, wreaking havoc across the country's vast supply chain involving roughly 200,000 workers.

JLR on Tuesday said it would extend its production halt until at least next Wednesday as it continued its investigation. In a statement, the company also cautioned that "the controlled restart of our global operations . . . will take time".

If JLR cannot produce vehicles until November, David Bailey, professor at University of Birmingham, estimated that the group would suffer a revenue hit of more than £3.5bn while it would lose about £250mn in profits, or about £72mn in revenue and £5mn in profits on a daily basis.

With annual revenues of £29bn in 2024, JLR will be able to absorb the financial costs but Bailey warned the consequences would be bigger for the smaller sized companies in its supply chain. JLR declined to comment.

The cyber attack comes at a crucial period for the UK carmaker when it is going through a controversial rebranding of its Jaguar brand and an expensive shift to all-electric vehicles by the end of the decade. Even before the latest incident, people briefed on the matter have said the company was facing delays with launching its new electric models.

"They are clearly in chaos," said one industry executive who works closely with JLR, while another warned that "no one actually knows" when production would resume.

"If there is a major financial hit, the CEO will look for significant cost savings to try and recover some of that, so that could hit both the production base in the UK but also its product development," said Bailey.

According to people close to the industry, JLR has been helped an ample inventory of JLR vehicles before the incident, meaning car sales were unaffected after production halted. The company is still able to sell new cars and register them manually.

According to online marketplace Auto Trader, JLR took the top slot on its new car platform in August and is vying for a similar position in September with almost a million ad views in the two months.

"Despite the well documented issues with the much-loved British brand at the moment, not only is there plenty of stock available but it's also drawing in the largest audiences in relation to its competitors," said Ian Plummer, chief commercial officer at Auto Trader.

Nevertheless, an immediate challenge for retailers has been their ability to source parts for car repairs. JLR has tried to secure additional supplies in response.

The company is also asking UK government officials to provide emergency support for its suppliers to get through this period, according to people close to the talks.

While JLR has not provided information on who is responsible for the attack, a hacker calling himself "Rey" has claimed to have infiltrated the carmaker's systems for the second time in just six months.

Cyber experts say they believe "Rey" is the same individual previously linked to the hacker group Hellcat, which claimed to have breached JLR in March and to have stolen confidential data. JLR declined to comment on the previous incident in March.

The organisation, which uses the same tactics as the "Scattered Spider" collective linked to the high-profile attacks on retailers, including M&S, has previously declared to have attacked companies such as telecoms group Telefónica.

The cyber attack at M&S in April forced the retailer to suspend online clothing and homeware sales for seven weeks -- a disruption expected to cost up to £300mn in operating profits this year.

Jaguar Land Rover's output could take several months to normalise, fear suppliers