The Labour leader, Jeremy Corbyn, has sent a barbed birthday card to Jeff Bezos to mark Amazon’s 25th anniversary, wishing the company “many happy tax returns” and demanding it pays more UK tax, pays its staff better and improves working conditions.

Amazon UK paid only £1.7m in corporation tax in 2017, its most recent annual public filing at Companies House, as pre-tax profits tripled to £72m. Turnover at its British business, which handles the packing and delivery of parcels and functions such as customer service, rose 35%, from £1.46bn to £1.98bn.

Corbyn’s birthday message to the world’s richest man, who has just finalised the world’s biggest divorce settlement, worth $38bn, says: “Dear Jeff. Happy Birthday. You owe the British people millions in taxes that pay for the public services that we all rely on. This year, pay your fair share of taxes, give your hard-working staff a pay rise and respect workers’ rights. Many Happy Tax Returns, Jeremy.”

Amazon insists it operates within the UK’s laws on corporation tax, which are based on profits not revenues, and that retail is a tough sector to make money in.

“We pay all taxes required in the UK and every country where we operate,” said a spokesman for Amazon UK. “Corporation tax is based on profits, not revenues, and our profits have remained low given retail is a highly competitive, low margin business and our continued heavy investment.”

The UK is Amazon’s third-biggest market globally in terms of retail sales, which are reported through a separate company in Luxembourg, with the company’s US filings showing that UK revenues hit $14.5bn last year, a 53% rise in only two years.

Robert Palmer, the executive director of Tax Justice UK, said: “People are fed up with companies like Amazon playing the system to slash their tax rate. We need to fix the broken global corporate tax rules that allow massive companies to pay little or no tax.”

The government is to introduce a new tax on the digital giants – including Google, Facebook and Amazon – from April next year to increase the amount they pay in the UK. A 2% tax on revenue from search engines, social media platforms and online marketplaces will be levied against technology firms that make more than £500m a year globally.

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Amazon, which has 17 warehouses in the UK and employs 27,500 workers, has also been accused of treating staff like robots and not respecting workers’ rights.

In May, trade unions lobbied City investors to put pressure on Amazon to improve conditions for its workers in the UK. The GMB told investors that workers at Amazon’s giant warehouses worked long shifts under pressure to hit targets for items picked, causing pain and injuries. Amazon workers’ allegations included lack of action on sexual harassment, unsafe working conditions and warehouse managers dismissing employees’ concerns and problems.

“Amazon employees already receive industry-leading pay and benefits and there are no zero-hour contracts in our fulfilment centres,” said Amazon. “We offer a safe, modern working environment.”