Widespread power cuts across Malta caused by a week-long heatwave have led to criticism of Prime Minister Robert Abela's government, with business fearing it could damage summer tourism on the island.

State-owned power company Enemalta said near record temperatures of between 40 and 42.7 Celsius (104-109°F) had caused electricity demand to spike and although it had ample power generation capacity, underground distribution cables were overheating and failing.

Business organisations said hours-long outages had caused supermarkets and restaurants to throw away food stock worth thousands of euros as fridges defrosted. Media showed pictures of empty shelves in a big supermarket.

The Health Ministry confirmed on Tuesday that Mater Dei Hospital, Malta’s central general hospital, was plunged into darkness on Monday night during a 35-minute power cut as generators failed to kick in, even though, it said, they had been tested on Monday.

An investigation is underway but the ministry said essential machines were kept running on batteries.

On Tuesday, the opposition Nationalist Party said nurses at a state-run mental hospital had to use torches on their mobile phones after generators at Mt Carmel Hospital also failed to work during a power cut a few nights previously. It described the situation as "disgraceful".

It also accused the government of spending millions on a "corrupt" deal to build a new power station while ignoring the problems of the distribution system.

The power station deal, signed in 2014, was later criticised in a report by the island’s auditor-general and is the subject of an inquiry by parliament's Public Accounts Committee.

An association which represents hoteliers, the MHRA, also criticised the government, saying the outages would have a long-term detrimental impact on tourism, a mainstay of Malta's economy.

It said many of its members had suffered financial losses because of lost food stock, cancelled bookings and damage to equipment running into thousands of euros. More importantly, they had suffered reputational damage.

The government has said it will consider compensation for damages and it will increase spending to improve the power distribution network. It has also offered elderly people affected by the power cuts free night accommodation in homes for the elderly, which are air-conditioned.

Malta Airport's meteorological office said it expects the heatwave to break by Wednesday morning when a north-westerly wind will bring down the temperature to around 34 degrees. (Reporting by Christopher Scicluna; Editing by Angus MacSwan)