A rightwing US group backing an anti-abortion campaigner whose case has become a new source of UK tensions with the Trump administration is significantly expanding activities and spending in Britain.

The UK branch of Alliance Defending Freedom (ADF), which is funding the case of Livia Tossici-Bolt – who is being prosecuted for an alleged breach of a “buffer zone” outside a Bournemouth abortion clinic – increased spending on campaigning and other activities in the UK to more than £1m last year.

ADF UK’s income was more than £1.3m in the year up to June last year, according to records filed to Companies House on Friday. It included “ADF support” of £1,119,975.

The organisation held discussions with a delegation from the US state department, which visited the UK last month before the release of a statement in which the US voiced concern about “freedom of expression in the UK”.

ADF UK, which describes itself as an advocate for “the right of Christians and others to freely associate and share their faith in public”, has been heavily involved in lobbying against the introduction of buffer zones around reproductive health clinics.

Its cases have included that of Adam Smith-Connor, who was cited by the US vice-president, JD Vance, as an example of free speech being under threat in Europe, after Smith-Connor was prosecuted for breaching a public space protection order.

Tossici-Bolt, ADF UK’s latest high-profile case, was mentioned in the US state department statement on Sunday.

A verdict on her alleged breach is expected on Friday. She denies the charges.

ADF, which is designated a hate group by the Southern Poverty Law Center in the US, has close links with Donald Trump’s White House after endorsing his election campaign and has spoken of working with his administration on areas including the reversal of trans rights.

The current speaker of the US House of Representatives, Mike Johnson, is a former ADF lawyer.

Filings show that the organisation’s British wing has a staff of nine, one earning a salary of £100,000 a year and two others paid between £90,000 and £100,000.

The same records give an overview of ADF UK activities in Britain, which range from briefing MPs to supporting campaigns against the assisted dying bill, and “free speech” cases.

The organisation is planning a big event in September in Britain as part of a plan to train law and public policy students.

ADF UK has five directors. Two, including the lawyers Robert Clarke and Paul Coleman, are based in the organisation’s international branch headquarters in Austria.

UK reproductive healthcare providers have voiced concern about ADF’s role and cited the reversal of abortion rights in the US and pressure exerted by rightwing campaigners.

Louise McCudden, the UK head of external affairs at MSI Reproductive Choices, said: “Before safe access zones were implemented last year, the behaviour we saw outside our clinics included spitting, calling women ‘murderers’ and physically blocking people from entering our clinics.

“In the US, abortion clinics have been bombed and burned down, and anti-abortion campaigners have been known to gather outside clinics with guns. Doctors have been assassinated.”

Heidi Stewart, the chief executive of the British Pregnancy Advisory Service, said: “It is deeply concerning that US anti-abortion extremists are using their significant financial resources to attempt to influence women’s access to safe, legal reproductive healthcare here in the UK.

“Following the overturning of Roe v Wade and the re-election of Trump as president, the anti-choice movement in this country have become emboldened in their continued attempt to strip women of their rights, dignity, and future.”

An ADF spokesperson said it was a registered human rights charity in the UK and was grateful to the US for bringing attention to what it described as the “free speech crisis” in Britain.

“We advance the right to live and speak the truth for all people and are proud to support Livia’s case and the cases of our other clients who have been victims of ‘buffer zone’ censorship,” they said.

ADF was named in a Facebook post by the US Bureau of Democracy, Human Rights, and Labor (DRL), an office in the US state department, as being among organisations its delegation met while in the UK.

It also met officials from the Foreign, Commonwealth & Development Office and Ofcom, using its talks with Britain’s communications regulator to challenge it on the impact of new online safety laws on freedom of expression.

The freedom of expression statement was issued after the delegation met Tossici-Bolt and ADF UK.

Among the group was Samuel D Samson, who previously worked for US conservative organisations and was pictured wearing a Make America Great Again cap. He was appointed as a senior adviser at the DRL in January. On the day of Trump’s US election, he tweeted: “Today we choose God over pagan idols.”

The DRL’s interest in Britain marks a pivot by an agency set up in the 1970s to advance democracy around the world against the backdrop of the cold war.