Rishi Sunak has reportedly restarted efforts to persuade the Japanese investor SoftBank to list the computer chip designer Arm in London. SoftBank has been considering listing Arm, which has its headquarters in Cambridge, for months, with New York thought to be the lead candidate. Arm produces designs for the chips embedded within 95% of the world’s smartphones. Before it was bought by SoftBank in 2016 it was a member of London’s FTSE 100 index, and its central role in the smartphone economy means it is seen as the most important British tech company. Sunak met the Arm chief executive, Rene Haas, and the chief legal officer, Spencer Collins, last month in Downing Street. Masayoshi Son, the founder of SoftBank, Arm’s Japanese owner, joined via video, according to the Financial Times. The UK government has pushed repeatedly for Arm to return to the London Stock Exchange, a move that would be seen as a vote of confidence in the UK. However, the UK lobbying has taken place under three prime ministers over the course of the last year of political turmoil. Andrew Griffith, the UK’s City minister, and executives from the London Stock Exchange are also involved in the talks with SoftBank, the FT reported. John Glen, a Treasury minister, met Arm and Softbank in June “to discuss Arm listing”, according to government disclosures. The government and regulators have made changes to the UK’s listing rules in an effort to persuade fast-growing tech companies that London is a worthwhile place to list their shares. Government officials have reportedly discussed a dual listing for Arm, which would allow it to trade in London and New York. However, dual listings come with higher complexity and costs. SoftBank paid $32bn (£26bn) for Arm in 2016 three weeks after the UK’s vote to leave the EU, which pushed down the value of sterling. The Japanese investor then sought to sell it in 2021 to the American chipmaker Nvidia. However, the $40bn deal collapsed after regulators expressed concerns. SoftBank’s next option was to seek a stock market listing but its plans were again stymied, this time by the global slump in the value of tech companies as interest rates rose. Arm’s head of investor relations last year wrote to private shareholders informing them of a delay to the listing plans, saying it was unlikely to happen until at least March 2023 because of “current global economic uncertainty” and “the state of financial markets”. However, he said the company was “fully committed to an IPO sometime in 2023”. Arm declined to comment. No 10 was approached for comment.