Emily Thornberry’s hopes of leading the Labour party are over after she failed to make it on to the final members’ ballot.

Just hours before the deadline closed on Friday night it became apparent that she would fail to get the backing from the required 33 constituency Labour parties to send her through to the last round.

It leaves the leadership contest as a three-way race between Keir Starmer, Rebecca Long-Bailey and Lisa Nandy.

Thornberry, the shadow foreign secretary, has struggled throughout the contest to get support despite her seniority in the party, receiving no union or socialist society backing – which is another way that would-be leaders can get through to the ballot.

By Friday night the Islington South and Finsbury MP only had the backing of 31 local parties and it appeared no more would declare before the deadline.

Late on Friday Thornberry tweeted her thanks to Cardiff North, which had swung behind her earlier in the evening.

However, the failure to convince other local parties means she will not get her name on the ballot paper that goes out to members, who have until 2 April to vote for who they want to succeed Jeremy Corbyn. She had staked her hopes on also winning the backing of several other local parties who were due to report on Friday night. In the event three backed Starmer and two backed Long-Bailey.

Thornberry thanked her campaign team as she acknowledged she would not be able to make it on to the ballot paper. She said: “I’m proud that I was the only candidate to secure nominations from all four nations of the UK, and I’m delighted to have made new friends around the country, and met so many dedicated campaigners, who may be deflated by the election result, but are determined to fight back.

“It was on their behalf that I stood for the leadership, because I’ve always believed we are at our best when – from the dispatch box to the doorstep – we are one, united fighting force, taking on the Tories, and standing up for the communities we represent.”

Thornberry had been travelling the length and breadth of the country for weeks, often representing herself at individual CLP hustings in a bid to secure nominations while other candidates chose to send a proxy in their place. Her backing from local parties was disparate – with strong support from some parties in the south-west, particularly Cornwall.

She had the support of just one party in London – her own. Guildford members also backed her. She had chosen to launch her campaign in the Surrey town where she grew up in a single-parent family.

Just hours before nominations closed, she wrote on Twitter: “Your CLP can make all the difference! Nominate me to get the widest range of voices, skills and experience on the ballot. Labour members deserve to have the widest and best possible choice when deciding our next leader.”

By 10pm on Friday it appeared 641 local parties had put forward their nominations. Starmer had 374, Long-Bailey had 164 and Nandy had 72.

Labour’s leadership rivals will significantly increase their campaigning efforts this weekend as they get access to party data allowing them to call thousands of members in an attempt to secure their votes.

The three remaining hopefuls are assembling an army of volunteers to help them reach the party’s grassroots.

Nandy won a major boost when members of the Labour affiliate Jewish Labour Movement gave her their backing after a hustings, saying she understood the need to change the party’s culture.

A source for Starmer’s campaign said: “Keir has been building a grassroots campaign with thousands of supporters across the country. Over the next few weeks the campaign will be taking the argument to the Labour movement about why another future is possible for our party and country.”

Labour’s central office will hand over names and phone numbers of members to all of the final-round candidates by 5pm on Saturday.

Labour’s grassroots group Momentum has been using its own data to run phone banks on behalf of Long-Bailey. Despite social media being an area of expertise for the leftwing group, it is said to be anxious about rivals ploughing significant resources into online campaigning.

A source said they were expecting her rivals Starmer and Nandy to “unleash big Facebook advertising operations”.

Nandy’s team includes the MPs Stella Creasy, Louise Haigh and Jonathan Ashworth, who will be helping to run phone contact sessions.

To make it on to the final ballot, the leadership hopefuls needed nominations from either 5% of constituency Labour parties, or affiliated unions and socialist societies.

Starmer won the backing of five trade unions, including a last-minute endorsement from the TSSA transport union. He also has Unison, Usdaw, Community and the Musicians’ Union.

Long-Bailey won the backing of Unite, with the general secretary, Len McCluskey, stating she had the “brains and the brilliance” to lead the party. She also won support from the CWU, FBU, Bakers Union and Aslef.

Nandy won backing from the GMB and the National Union of Mineworkers.