Britain's high streets reported their worst May on record as sales collapsed 3.3% compared with last year, figures show.
The drop, following a fall of 2.2% for May last year, is the fourth month in a row of poor results, according to BDO's High Street Sales Tracker (HSST).
Sophie Michael, head of retail at BDO, said: "Our high streets are creaking at the seams. It's time the Government took action and showed some much-needed support for retailers and to the millions of people the sector employs.
"Both retailers and shoppers alike need a clear roadmap that can deliver much needed confidence for the future.
"Retailers know they need to adapt their physical portfolios and respond quickly to changing consumer behaviours, but they are in investment paralysis as Brexit uncertainty drags on and consumer confidence remains low.
"It is vital that the ambivalence with which the high street is currently being treated is replaced with concerted action, or the results could be catastrophic."
Lifestyle shops were among the worst hit - with a 2.4% from in in-store sales from an already negative position of -3.8% in May last year. There has been no growth in the sector for 16 months.
Fashion sales in store also fell 4.2% - compared to a 0.4% increase in the same month last year.
BDO said the figures reflected how difficult the trading environment had become for retailers.
They follow the British Retail Consortium warning that the high street saw its biggest decline since the mid 1990s last month after overall retail sales fell by 2.7%.
