The boss of B&Q owner Kingfisher has sounded the alarm over the risk of a business rates raid on larger stores in next month’s Budget.

Thierry Garnier joined a chorus of retail chiefs in urging Labour not to hit big premises as part of reforms to the hated commercial property tax.

Garnier said: ‘Big stores are very often big anchors in retail parks and in high streets, large employers in cities. So we very much hope that the larger stores won’t be penalised in the coming weeks.’

The comments came as Kingfisher – which also owns Screwfix as well as European brands Castorama and Brico Depot – upgraded its full-year profit outlook after publishing strong first half results.

That was despite a setback for B&Q, which saw summer sales hit by the heatwave and weak demand for its bathroom range, which is now being revamped. Instead, customers preferred to splash out on their kitchens.

Garnier said: ‘People are spending more money on their kitchen today than on their bathroom… a more important part of our lives, it’s becoming a more important room in the house, and we see that across Europe – a more positive trend on kitchen than bathroom.’

Shares rose 9pc in early trading as the UK-listed group said adjusted profits for the six months to 31 July rose 10pc to £404m, driven by higher margins and cost control.

It is now forecasting full-year profits of £595m-£635m, versus previous guidance of £565m-£625m.

However, like-for-like sales rose by just 0.3pc and Garnier admitted that ‘the consumer environment remains mixed’.

In the UK, Screwfix sales jumped 5.6pc in the first half but B&Q struggled, with a fall of 2.9pc. The brand saw a notable 8.1pc slump in demand for ‘big ticket’ items in the second quarter.

Screwfix has more than 981 stores in the UK and Ireland while B&Q has 318. 

Garnier, who is quitting Kingfisher to become the boss of Netherlands-based supermarket group Ahold Delhaize shrugged off a question about his departure.

He said: ‘I’m fully committed and focused on Kingfisher. The board has a well-prepared succession plan. The search is ongoing and moving at pace.’

On the Budget, Garnier said: ‘We believe that retail is a powerful engine for growth, it is an engine of employment, and we hope the government can see it in the same way.

‘Stability and certainty is always what you look for as a business.

‘For us, the number one priority is business rates… in the longer term, we need a level playing field between bricks-and-mortar and online players.

‘When you are a brick and mortar retailer and when you are a pure online company you don’t pay the same tax and that will create more and more issues in the future.’

But his fears over the impact of business rate hikes on larger stores echo those expressed by the bosses of other major retailers in recent weeks. 

Sports Direct billionaire Mike Ashley has said the Government would be ‘simply delusional’ to heap more pressure on big retailers.

Some firms fear Prime Minister Andy Burnham and Chancellor John Healey are plotting a fresh business rates raid on large shops to fund lower bills for pubs and music venues.

They are particularly concerned that rates paid by large stores, which are deemed to have a rateable value of £500,000 or more, will be increased.

Outgoing John Lewis boss Peter Ruis said earlier this month that it would have ‘a terrible impact for all retailers’.