Tesco is to be hit with a threefold increase in the money it pays to finance the Groceries Code Adjudicator, despite seeing by far the biggest improvement in its behaviour of all the supermarkets.

Christine Tacon today revealed new plans to vary the levy paid by supermarkets based on their size and the amount of work she estimates spending on probing issues about them.

Tesco’s share of the levy will jump from £100,000 to £302,000, a year after it was investigated by Tacon, who found the supermarket guilty of serial breaches of the code.

However, a YouGov survey released by the GCA today found 65% of suppliers thought Tesco had improved its behaviour in the past year. Tacon even singled out Tesco saying there had been a “complete culture change driven from the top”.

Iceland was the second-biggest improver, with 26% saying it had got better at observing the code in the past year.

Tacon’s Tesco raid comes on top of her doubling the overall levy this year paid by supermarkets to £2m, as revealed by The Grocer earlier this year.

Tesco will be asked to pay 17% of the entire levy compared with the smallest supermarket paying just 8%.

Suppliers rated Aldi, Sainsbury’s and Lidl as the top three supermarkets with Asda and Morrisons behaving the worst over the past year.

The poll showed nearly a quarter of suppliers at both supermarkets thought their practices had worsened in 2016.

Tacon said she had experienced most issues with Morrisons, which The Grocer revealed last week had shown the door to several employees after a probe by Tacon into lump sum payments being demanded of suppliers.