Two key Tory strongholds could be on course for Labour victories in a shock election swing, according to new modelling.

Wandsworth and Barnet councils could both swing Labour after decades of Tory leadership at the local elections next week. 

Forecasters at Britain Elections, the New Statesman's election calendar, have modelled a fresh map of what political control could look like in London after the elections. London will go to the polls to vote in new councils on May 5 for the first time since 2018. 

The map predicts both Wandsworth and Barnet turning red – key targets for opposition leader Keir Starmer. Wandsworth Council has been controlled by the Tories since 1978, while Barnet Council has never been fully held by Labour since its creation in 1965. 

The new model is based on a recent Opinium poll for Sky News, which found support for Labour had gone up by just one point in London since 2018. But after mapping the data, taking into account boundary changes, pollsters at Britain Elections said there will be "a lot of churn and seats changing hands". 

The Conservatives could lose up to 71 seats, while Labour could make a net gain of 38 seats. The Lib Dems could increase its number of seats in London by nine, and the Greens by a net total of five. The map sees the Tories lose Wandsworth and Barnet out of the handful of councils the party still controls in the capital.

Wandsworth is well-known for its comparatively low council tax, which its Tory-led council claims is the lowest average council tax in the UK. The council adds that it has frozen its rents for council tenants, heating and hot water fuel charges. But anger over Partygate and the cost of living crisis could see Labour end the Tories' 44-year control of Wandsworth in May. 

The hotly-contested by-election in November for the council's Bedford ward seat suggests the results could be tight. The seat was won by Labour by just one vote following the resignation of Independent ex-Labour councillor Hannah Stanislaus. 

Simon Hogg, Wandsworth Labour leader, said: "The election in Wandsworth will be decided by a handful of votes in a few key wards. Labour is working hard to earn every vote so we can create a compassionate council that truly listens, that builds genuinely affordable homes and a safer, greener Wandsworth."

A spokesperson for Wandsworth Council Conservatives said the group delivers "top-quality services and the lowest average council tax in the UK – giving residents a better deal with excellent council services for half the cost that neighbouring Labour-run boroughs charge". 

The spokesperson said: "Wandsworth Council Conservatives have frozen council rents, heating and hot water charges for over 3,000 council tenants and leaseholders – helping those with the least the most. 

"Wandsworth Council Conservatives can only do this because of four decades of sensible financial management."

The Evening Standard reported this week that Labour has built a 27-point lead over the Tories in London overall. The YouGov survey for Queen Mary University of London's Mile End Institute puts Labour at 50 per cent, more than double the Conservative's figure of 23 per cent.

The survey puts the Lib Dems on 12 per cent and the Greens on nine per cent. 

Dr Patrick Diamond, Director of QMUL's Mile End Institute, said: "Our new research shows that Labour is set to perform significantly better than the Conservatives in the forthcoming London borough elections.

"Support for the Conservatives across the city has fallen sharply since the local elections in 2018, however, Labour's vote does not look set to advance beyond its successes that year, when it performed particularly strongly."

Thousands of seats across the country are up for grabs in the local elections on May 5, including councils in all London boroughs.