More than a third of orders for goods placed via the internet cause problems - including fraud, misplaced or forgotten orders and late deliveries - according to the Institute of Trading Standards.

In one study officials had difficulties with 38 per cent of their orders. In another, they found that 25 per cent of websites were insecure.

Jennifer Mundie, a market trader of Mintlaw, Aberdeenshire, ordered £554 of Pokémon goods from a Chinese website. She realised she had been defrauded when customers returned the children's toys complaining they were fake. 'I felt terrible,' she said after refunding the cash. 'I felt like a criminal because I had sold these items, when in fact I was a victim.'

Other dotcom victims were Phil Dart and Karen Gianfreda. After buying a Caribbean holiday worth £2,700 on the web they arrived at their island resort to find one beach (not two as advertised) strewn with signs warning of falling rocks, poisonous fruit and tree sap that caused skin blisters. Swimming in the sea was not allowed and an advertised roller-blading track did not exist.

In the first survey, trading standards officials tried to make purchases through 102 British-based internet sites. Some sites veered towards the fraudulent. One officer tried to buy a penknife from a company based in south-west England only for the site to crash after credit card details had been entered. A postal address and telephone number given on the site were false. 'The firm only existed on the internet,' said Simon Cripwell, a trading standards spokesman.

For 17 per cent of orders, goods simply failed to appear, either forgotten, out of stock or blamed on 'system crashes'.

Most consumer worries about internet shopping have focused on security and giving credit card details over the net. The second survey, of 70 sites, found such concerns are justified: a quarter of sites investigated were insecure - credit card data were not encrypted before being transmitted. Officers also expressed concerns about inaccurate price information and misleading advertising on a third of these 70 sites.

'Just as you would avoid disreputable-looking shops in the high street, so you should avoid sites on the internet which look dubious,' said Alan Stevens, in charge of internet-based training for the Consumers' Association. Shoppers should steer clear of sites which ask for credit card details by e-mail or which do not give a telephone number or physical address. A failure to respond to e-mail enquiries is also a bad sign.

The CA runs a 'kitemark' scheme whereby internet sites that have met security standards and abide by an accepted code of commercial practice display a red and grey coloured ' Which? Web Trader' logo.

Reduce the risks: how to minimise the dangers of being defrauded when internet shopping:

* Don't give credit card details by email.

* Avoid buying from sites that don't give a telephone number or physical address.

* Look for the Consumers' Association kitemark, the ' Which? Web Trader' logo.