Lewisham Council is asking Greenwich Council to start paying towards the annual Blackheath fireworks display again, after revealing fundraising for this year’s event fell nearly £30,000 short of covering its costs.

Greenwich withdrew its £37,000 share of funding for what was a jointly-run display in 2010, with council deputy leader Peter Brooks claiming it would be “inappropriate in this financial climate” to fund the event, which takes place right on the border between the two boroughs.

But Lewisham has continued to hold the event, which attracts up to 100,000 people and boosts trade to local businesses in Greenwich, Blackheath and Lewisham.

Lewisham has continued to set aside £36,000 each year for the display, which this year cost £108,673, and has relied on public donations and private sponsorship to make up the rest.

But a cut in private sponsorship money this year has meant the shortfall has widened from £7,919 to £29,656 this year, according to an answer from Lewisham’s culture and community services cabinet member Chris Best given at a council meeting last Wednesday.

Responding to Blackheath councillor Kevin Bonavia, she said in a written reply: “Officers continually look for different ways to attract funding for the event. We will continue to request financial and other support from the Royal Borough of Greenwich.”

At the time Greenwich Council’s Peter Brooks was claiming the borough was too hard-up to pay for Blackheath fireworks, Greenwich was paying £30,000 each year on a private party to inaugurate the borough’s ceremonial mayor.

While that cost has come down to £10,000 – thanks to the Royal Naval College no longer charging – this summer the council contributed £20,000 to fireworks displays to support Sail Royal Greenwich, a private company working out of the council’s Mitre Passage offices in North Greenwich.

In 2011, it effectively bailed out Greenwich and Docklands Festival with a £100,000 payout, and spent £110,000 on events to mark becoming a royal borough in 2012.

And while supporters of leader Chris Roberts point to Lewisham’s controversial decision to cut library funding in response to a government funding squeeze, Greenwich has been cutting under-fives’ play centres, outsourcing youth and library services and trying to cut funding from Charlton’s Maryon Wilson animal park.

Relations between the two Labour groups have got worse recently, with Lewisham councillors looking on in alarm at the bullying accusations levelled at Greenwich leader Chris Roberts, with the bad smell drifting across the border.

Greenwich councillors complained to their Lewisham counterparts after Bonavia referred to the accusations in his unsuccessful campaign to be the parliamentary candidate for Greenwich & Woolwich, demanding he be disciplined for disloyalty. They were flatly turned down.

Lewisham council also reaffirmed its reservations about the proposed Silvertown Tunnel – which is backed by Greenwich – at the same meeting.

Deputy mayor Alan Smith said: “The proposed Silvertown Tunnel relies on the same southern approaches as the existing Blackwall Tunnel. These routes, including the A2 area and the South Circular, already suffer from daily congestion. As the only primary alternative to the Dartford crossings, these routes come under extreme pressure when the M25 is not operating smoothly. The council therefore has reservations about the impact of an additional 6,000 vehicles per hour on these routes.”

Other London boroughs, including Southwark, Tower Hamlets, Barking & Dagenham and Redbridge, have also voiced opposition or reservations about mayor Boris Johnson’s plan. In the affected area, only Greenwich and Tory Bexley are wholly for it.