UK arms manufacturers have exported almost £5bn worth of weapons to countries that are judged to have repressive regimes in the 22 months since the Conservative party won the last election.

The huge rise is largely down to a rise in orders from Saudi Arabia, but many other countries with controversial human rights records – including Azerbaijan, Kazakhstan, Venezuela and China – have also been major buyers.

The revelation comes before the Defence and Security Equipment International arms fair at the Excel centre in east London, one of the largest shows of its kind in the world. Among countries invited to attend by the British government are Egypt, Qatar, Kenya, Bahrain and Saudi Arabia.

Campaigners called on the government to end arms sales to the United Arab Emirates in light of its record on human rights. They accused the government of negotiating trade deals to sell the Gulf state cyber surveillance technology which the UAE government uses to spy on its citizens, and weaponry which, they allege, has been used to commit war crimes in Yemen.

The Saudis have historically been a major buyer of British-made weapons, but the rise in sales to other countries signals a shift in emphasis on the part of the government, which is keen to support the defence industry, which employs more than 55,000 people.

Following the referendum on leaving the European Union, the Defence & Security Organisation, the government body that promotes arms manufacturers to overseas buyers, was moved from UK Trade & Investment to the Department for International Trade. Shortly afterwards, it was announced that the international trade secretary, Liam Fox, would spearhead the push to promote the country’s military and security industries exports.

Activists protest against the Defence and Security Equipment international arms fair at the Excel centre in London. Photograph: Ollie Millington/Getty Images

But charities and other organisations that campaign against the arms trade fear that a post-Brexit Britain will see an increase in weapons sold to countries with poor human rights records.

Last week Labour MP Helen Goodman questioned why the UK had exported £80,000 worth of arms – believed to be components for submarine systems – to the Maduro government of Venezuela in the past year. Goodman asked: “In light of the Maduro government’s refusal to cooperate with the ongoing UN-led investigation into human rights abuses, will the government suspend any further arms sales until those concerns are resolved?”

Campaign Against the Arms Trade has found that of the 49 countries that are classed as “not free” by Freedom House, the independent organisation that promotes democracy, 36 have bought British-made weapons under the current government.

Since 2015, Saudi Arabia has agreed orders for more than £3.75bn worth of British defence equipment – mainly bombs and fighter aircraft – up from £160m in the 22 months leading up to the election. Even when Saudi’s massive order book is stripped out, arms exports to repressive regimes have almost doubled since the Tory government was elected: orders to such countries, excluding Saudi, amount to almost £1.2bn, compared with £680m in the 22 months before the election.

Among the major buyers were: Algeria, which agreed a military helicopter deal in September 2015, worth £195m; Qatar, which is buying military support aircraft worth £120m; and China, which is subject to an arms embargo. Despite the embargo, the UK agreed a £16m deal to export components for military radar. One notable new customer is Azerbaijan, which bought £500,000 of “targeting equipment”.

“The UK has consistently armed many of the most brutal and authoritarian regimes in the world, and a number have been invited to London to buy weapons,” said Andrew Smith of Campaign Against Arms Trade. “These arms sales aren’t morally neutral, they are a clear sign of political and military support for the regimes they are being sold to. The government has played an absolutely central role, and has consistently put arms exports to despots and dictators ahead of human rights.”

The government insists that its arms export licensing systems is subject to stringent rules. Foreign Office minister Alan Duncan told parliament last week: “The government take their export control responsibilities very seriously and operate one of the most robust defence export control regimes in the world. We rigorously examine every application case by case against consolidated EU and national arms export licensing criteria.”