Mushrooms instead of tampons and cream crackers in place of Christmas crackers are among the unusual substitutions online shoppers say they have been sent.

The strangest swaps were revealed in poll, commissioned by Which?, which also found that a third of customers were sent a ‘sub’ in their most recent online grocery shop.

Asda, suggests the survey of more than 3,000 people, was found to be the worst offender with more than half of customers receiving a replacement item in their last order.

Among the strangest substitutions delivered in the last year was fruit-scented shower gel sent instead of fresh fruit while another hoping for washing powder opened the door to 10 cans of beer.

Two in five Sainsbury’s customers said they had a substitution in their latest shop – with one bemused customer taking delivery of allergy tablets instead of their new anti-allergy duvet, while another hoping for a loaf of bread was sent flour.

When it came to Morrisons’ - a third claimed to have had a substitution in their most recent grocery order – with one hungry customer recalling onions being sent when their cheese and onion crisps were unavailable.

Tesco too, is said to have sent subs to around a third – where Christmas prep didn’t quite go to plan for one customer who was delivered cream crackers instead of the Christmas crackers they were after. Another claimed a ready meal was substituted for a salad.

For those using online services at Aldi – one surprised shopper bagged fruit sweets instead of their order of fruit salad – while at Waitrose, where a quarter of customers had been sent a sub in their last shop, one customer claimed to have been sent meat sausages as a replacement for the vegetarian ones requested.

At Iceland, where a frozen pizza arrived instead of a tin of peaches, a quarter of those surveyed said they had substitutes in their last shop.

Ocado shoppers were the least likely to receive a sub – with just one in six having been sent one in their last order – however when asked about the strangest substitutions one customer admitted to receiving mushrooms instead of tampons.

While grocery substitutions can be a nuisance, particularly for those missing an essential item or a component for a recipe, Which? says the implications can be more serious for those with a dietary need or allergy.

Several shoppers, says its poll, took delivery of items unsuitable for them including lactose-free cheese being replaced with regular cheese and a switch from two vegetarian ready meals to those containing meat.

Ele Clark, Which? Retail Editor, said: “If the item you’ve ordered is out of stock, well-chosen substitutions can be really handy - but our research has shown that all too often the replacement item is inappropriate or downright bizarre.

“Shoppers have the right to reject substitutions at the point of delivery, or you can sometimes opt out of receiving substitutions altogether. If you end up with an unwanted substitution after the driver has gone, contact the supermarket and ask for a refund - some have handy online tools to make the process easier.”