Will trade union contests help or hinder Keir Starmer?

On Monday, the new general secretary of the UK's biggest union - Unison - will be announced.

Under its outgoing leader Dave Prentis, the union backed Sir Keir Starmer's successful Labour leadership bid.

And Sir Keir can currently rely on support from the union's representatives on Labour's ruling National Executive Committee (NEC).

The outcome of the contest could have consequences for that support.

The expectation is that one of the assistant general secretaries, Christina McAnea, will prevail and become the first woman to lead the union.

She has a strong background as a negotiator and has shown little interest in internal Labour politics, but is expected to be broadly supportive of the party's current leadership.

But the outcome isn't certain.

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She has faced a strong challenge from another assistant general secretary - Roger Mackenzie - who has the backing of former Labour leader Jeremy Corbyn.

He hopes to be the first candidate from a BAME background to take the top job.

His chances of victory may be undermined by the fact that two other candidates - Paul Holmes and Hugo Pierre - have also been competing for the Left vote.

But, Mr Mackenzie's campaign was given a fillip when Mr Corbyn was suspended from the Parliamentary Labour Party, giving him a defining rallying cry.

And developments are expected soon in the country's second biggest union - Unite.

Unite divided?

Unite is the biggest trade union funder of the Labour Party so whoever succeeds Len McCluskey as general secretary could determine how generous, or otherwise, it is in its contributions.

Mr McCluskey still has not announced exactly when he will stand down and can stay in office until next year, but the election contest to succeed him is expected to take place this year.

While the potential successors have agreed not to campaign openly, insiders say there has been something of a "phoney war" going on.

The United Left faction is backing Steve Turner, an assistant general secretary who has declared he does not want "a war of attrition" with the Labour leadership.

Len McCluskey is due to stand down in 2022

Another assistant general secretary - Howard Beckett - complained that there were irregularities in the United Left ballot which backed Mr Turner and he will challenge for the top job from the Left.

Unlike Mr Turner, he has been an outspoken critic of Sir Keir and is one of the union's representatives on Labour's NEC

He led a left-wing walkout (or a zoom 'switch off') from the NEC in November, denouncing what he called "Keir Starmer's factionalism".

He and his colleagues were not just unhappy at Mr Corbyn's treatment by the party leadership but the elevation of another Beckett - Dame Margaret - to the chair of the NEC rather than a more left-wing member, trade unionist Ian Murray.

But it seems another candidate in the forthcoming Unite contest is about to emerge.

Workers' Unite

Next week, I'm told, a new grouping in the union will be formed - Workers' Unite.

This grouping - made up of grassroots activists - is likely to morph in to a campaign to support Sharon Graham when a formal contest gets under way.

She has said she would stand when there is a vacancy.

She is the union's executive officer for "organising and leverage", who has overseen successful industrial disputes and would be the first female general secretary were she to succeed.

Sharon Graham is expected to throw her hat in the ring

One of the leading figures behind Workers' Unite is Kathy Smith, a member of the union's executive representing local government workers.

She told the BBC that Sharon Graham "would be a breath of fresh air" at the top of the union.

According to its launch literature, a major theme of the Workers' Unite campaign will be to "move beyond internal Labour Party politics" and "to always prioritise the workplace".

That is likely to be met with relief by those around Sir Keir.

Gerard Coyne is said to be considering joining the race to take over from Len McCluskey

Sharon Graham and supporter Kathy Smith are both on the Left.

But Ms Smith believes any campaign for the leadership of the union would appeal beyond that base by focusing on "the members' priorities: jobs, pay and terms and conditions. Not contemplating our belly buttons."

And she argues that Ms Graham's willingness not just to negotiate with big employers - such as British Airways - but to stand on picket lines in local disputes will help build solid support among grassroots activists.

The candidate Len McCluskey beat in the Unite leadership election in 2017 - Gerard Coyne - has thrown his hat in the ring again.

Seen as an anti-Corbyn candidate by many members of Labour's parliamentary party last time round, he unsuccessfully challenged the union's internal electoral processes following his defeat in what was a particularly bitter contest.

But if the Left territory in the union is going to be fought over, Mr Coyne seems to have calculated that he could - in a first-past-the-post contest - prevail.