Theresa May’s championing of arms exports to Turkey is consistent with a policy promoted by a succession of trade ministers, but will soon haunt the government in the courts.

For more than a decade Britain has been seeking to expand its arms exports to a number of new partner countries, some of which have deeply questionable human rights records.

Turkey, which has imprisoned tens of thousands in the wake of last year’s failed coup, was made a priority market by trade ministers as far back as 2009. The country’s elevated status has seen UK officials spend considerable time, money and resources wooing their Turkish counterparts.

Documents released under the Freedom of Information Act, confirm that UK officials have made regular trips to the country to foster relations and have played host to Turkish military officials at major arms shows in the UK. Other priority markets courted assiduously include Saudi Arabia, Bahrain and the United Arab Emirates – all of them countries that have been criticised by human rights groups.

The new £100m deal, which will see the defence giant BAE Systems develop new fighter jets for the Turkish military, suggests that the May government, operating with one eye on Brexit and the urgent need to expand trade agreements, intends to be even more enthusiastic than its predecessor when it comes to the licensing of arms exports.

Last week the Observer reported on newly released figures showing that between July and September last year, shortly after last year’s failed coup triggered a crackdown by the country’s security forces, the UK issued almost £50m worth of licences for arms exports to Turkey. This has taken the total value of licences issued since 2015 to more than £330m. At least 117 UK companies have applied for military export licences to Turkey in the past five years.

A 2015 briefing from the Department for International Trade Defence & Security Organisation suggests the UK could cut deals with Turkey on projects including unmanned drones, logistics and training support for transport aircraft and an F-35 Joint Strike Fighter: “With increasing budgets and the second-largest army in Nato, there are opportunities for UK industry.”

But the sale of arms to Turkey will prove deeply controversial. Since the Kurdish conflict re-emerged in 2015, there have been “mounting civilian deaths and multiple rights violations”, according to Human Rights Watch.

The coup attempt has led to more than 125,000 people being dismissed or suspended from their jobs, with about 40,000 others arrested. There are claims that opponents of the regime have been tortured. Some 130 media outlets have been shut down.

“The human rights situation in Turkey has only got worse since [President] Erdoğan came to power,” said Andrew Smith of Campaign Against Arms Trade (CAAT). “The crackdown has intensified, and so has the war on journalism, yet Theresa May has shown she is willing to turn a blind eye to these abuses in order to secure arms company profits.”

Pax, an organisation that campaigns for an end to armed violence, said that arms transfers to Turkey went against the international obligations of EU member states. It said arms sales, “especially to its land and air forces, should be halted until real progress is made towards a political solution with the Kurds. In the context of current EU-Turkey relations, a freeze in arms sales would be a logical and necessary step, in line with the obligations EU states have with respect to the common position on arms exports, as well as under the UN arms trade treaty”.

The UK insists that all arms sales, including to Turkey, are thoroughly vetted and made to comply with strict export criteria and international obligations. But this position could be shredded next week when the high court hears a judicial review into the legality of the UK selling arms to Saudi Arabia that have been used in the bombing of Yemen. The review follows an application by CAAT, which claims that UK arms have been central to the devastation of Yemen and the humanitarian crisis it has caused.

Smith said: “Our legal action is focused on arms exports to Saudi Arabia and the devastation they have unleashed on Yemen, but it could set a vital precedent in challenging arms exports to human rights abusers across the world.”