The RHS Chelsea Flower Show is to lose its headline sponsor, while the number of big-budget Main Avenue show gardens at this year’s show on 23-27 May (2017) will fall by almost half.

After Chelsea 2017, M&G Investments will terminate its backing of the world’s most famous flower show, following eight years of sponsoring the floral extravaganza.

In a blow to Chelsea visitors, there will only be nine Main Avenue show gardens this year (2017), compared to 17 in 2016, despite tickets to Chelsea costing up to £72.

It is understood that city corporations have been reluctant to sponsor Main Avenue gardens, rumoured to cost around £250,000 each, due to economic uncertainty ahead of Britain’s divorce with the EU. The Daily Telegraph has pulled out of Chelsea while Irish designer Diarmuid Gavin is taking a break to focus on other projects.

An RHS spokeswoman confirmed there would be just nine Main Avenue gardens but added: “With an increase in the number of smaller gardens at the show, there will be six less gardens in total across all categories. We are considering other content for the 2017 show, but at RHS Chelsea it will always be about quality and not quantity.”

The RHS confirmed it will part company with M&G after Chelsea in May. The spokeswoman added: “After eight successful years as sponsor of RHS Chelsea, M&G has decided to look at other ways of investing in its brand profile at the end of the contract term after the 2017 show.

“We would like to thank M&G for such fantastic support over so many years, and hope to continue our relationship with them after this year’s show.

The RHS said Chelsea sponsorship had helped the charity to “bring gardening to more than six million children through the RHS Campaign for School Gardening.”

Asked about rumours that the Chelsea sponsorship deal is a “substantial seven-figure sum,” the RHS replied: “We do not discuss financial details of sponsorship agreements as they are commercially sensitive.

“M&G is the sponsor of Chelsea 2017, so we will not be in a position to discuss plans for 2018 onwards for some time.”