In an attempt to exploit Labour's divisions over Trident, the SNP today tabled a motion opposing its renewal. Labour whips instructed MPs to abstain on the grounds that the vote was "a stunt", as John McDonnell told reporters outside last night's PLP meeting.

But in defiance of the leadership, 14 backed the renewal of the nuclear deterrent. Their justification was clear: it remains official party policy to support Trident after annual conference voted not to debate the issue (a point made at the PLP by Ben Bradshaw, Chris Leslie, Jamie Reed and John Woodcock). For them, Labour's credibility depends on it maintaining its backing for the programme. By contrast, six MPs voted against renewal, the cost of which was revealed by yesterday's Defence Review to have risen from £25bn to £31bn.

The SNP is, unsurprisingly, delighted at having divided Labour. Defence spokesman Brendan O'Hara said: "For Labour, today was a sign of their moral bankruptcy in the Trident debate. Astonishingly for a party that say they want to govern, some of their members abstained, some voted with the SNP and some even voted to support the Tory nuclear folly. Labour’s solitary Scottish MP Ian Murray abstained – despite voicing his opposition to Trident renewal. His leader Jeremy Corbyn also abstained – although he previously supported an identical SNP motion in January this year. This is just the latest evidence that Jeremy Corbyn isn’t changing Labour – Labour is changing him."

A potentially far greater division lies ahead when parliament votes on renewal. Many Trident supporters abstained today but would not do so on the official decision. With the majority of the shadow cabinet in favour of renewal (unlike their leader), most frontbenchers expect Corbyn to offer a free vote. Andy Burnham, the shadow home secretary, has pledged to resign if the party opposes Trident renewal and others would likely follow. Among the most committed supporters of the deterrent are the deputy leader, Tom Watson, the shadow culture secretary, Michael Dugher, and the shadow Northern Ireland secretary, Vernon Coaker. But with Corbyn and his supporters arguing that he has a mandate to oppose renewal, and floating the idea of an online ballot of party members, today's split is but a hint of the divisions to come.

The 14 Labour MPs who voted in favour of Trident

Kevin Barron (Rother Valley)

Ben Bradshaw (Exeter)

Mary Creagh (Wakefield)

Chris Evans (Islwyn)

Jim Fitzpatrick (Poplar and Limehouse)

Liz Kendall (Leicester West)

Chris Leslie (Nottingham East)

Madeleine Moon (Bridgend)

Albert Owen (Ynys Mon)

Jamie Reed (Copeland)

Emma Reynolds (Wolverhampton North East)

Angela Smith (Sheffield Hillsborough)

Gisela Stuart (Birmingham Edgbaston)

John Woodcock (Barrow and Furness)

The six Labour MPs who voted against Trident

Ronnie Campbell (Blyth Valley)

Roger Godsiff (Birmingham Sparkbrook)

Kelvin Hopkins (Luton North)

Geoffrey Robinson (Coventry North West)

Dennis Skinner (Bolsover)

Graham Stringer (Blackley and Broughton)