The economic aftershocks from last month's Japan earthquake reached British industry today when Honda halved production at its Swindon car manufacturing plant due to a shortage of components.

The destruction wrought by the earthquake, tsunami and power station failure at Fukushima has disrupted the manufacture and export of parts ranging from satnavs to brakes, paint and computer chips, and is now hitting dozens of car factories worldwide. Honda has announced that the 3,000 workers at its Swindon factory will work two days a week until the end of next month as production falls to around 300 cars per day.

Neil King, analyst at IHS Automotive, said around 1m fewer motor vehicles could be produced worldwide this year due to the Japan earthquake. He added that Japanese manufacturers faced the threat of sales losses in key markets if they did not repair the damage quickly.

"It's a question of how quickly they get things up and running. If a dealer offers you a delivery within months, whereas one across the road says it will be weeks, it is possible that the customer might switch," he said.

King also pointed out that Japanese parts suppliers also sold to non-Japanese manufacturers, which could affect other automotive groups whose state-of-the-art production processes still rely on thousands of parts, often sourced from abroad. "There are typically around 20,000 components in a car and all it only needs one to be missing to halt production," he said.

A spokesman for Honda said the cutbacks were "responding to the parts supply situation, while trying to maintain a supply of new cars to customers, particularly in the UK." He added: "By keeping the production level at two days per week we will maintain a flow of new models to the UK market." The UK is Honda's largest European market.

A trade union official warned that production levels at the Swindon plant could change further because the parent company is still gauging the scale of the damage to its operations. Jim D'Avila, an officer with the Unite trade union, said: "I will not be upset and surprised if they have to deviate from what they told us today because the information coming from Japan is so difficult to translate in terms of whether we can build cars or not."

He added: "There was no quality information getting back. Car parts were being shipped only part-way and communications were at a halt."

Honda staff will remain on full pay and are negotiating a bonus for meeting the UK production target of 135,000 vehicles, which has not been dropped. The Japanese manufacturer has invested £1.4bn in its Swindon operation, which started building engines in 1989 and cars three years later.

Elsewhere in the UK, rival Toyota has halted daily overtime and cancelled three Saturday shifts at its plant in Burnaston, Derbyshire, where 2,600 staff produced 137,000 cars last year. A spokesman said there could be further disruption. "Some parts do still come from Japan and we are still assessing the situation."

In Japan, Toyota has already lost the equivalent of 260,000 vehicles due to a 20-day suspension at most of its 18 domestic factories, although it has restarted limited production of its hybrid Lexus and Prius models. Toyota has also admitted that "some production interruptions" are likely at its 14 plants in North America.

Moody's, the credit ratings agency, has warned that it might downgrade the Toyota group because of the earthquake's financial impact. The agency said its decision will be based on how quickly Toyota can restore production in Japan, which could take months. "Moody's will also consider how quickly the company can improve its profitability despite the negative impact of the disasters," it said.

Nissan, whose 4,900 Sunderland-based employees produce more than 420,000 cars per year, said UK production had yet to be affected.