Big Six energy provider SSE today became the latest firm to announce a cut in gas tariffs but said the move would not take effect until April 30.

The UK's second biggest supplier faced criticism for the delay which means customers will still be paying higher tariffs when energy usage is highest and tariffs will not come down until the milder period in the spring.

SSE said it was also extending its price freeze on gas and electricity bills until at least July 2016.

The supplier hiked dual fuel prices by 8.2% in November 2013 before cutting them in March last year by 3.5% in response to industry changes and then pledging a freeze which it initially said would last until January.

SSE said today's 4.1% cut, which is in response to the falling cost of wholesale energy, would save a typical household customer £28 a year.

It will take effect much later than those announced by rivals - with biggest supplier British Gas cutting prices by 5% from February 27 while E.ON lowered tariffs by 3.5% immediately from January 13.

Scottish Power and npower have also announced price cuts, with EDF, the only supplier which has not yet done so, now likely to come under pressure.

Price comparison website moneysupermarket.com accused SSE of making "April fools" of customers by delaying its price cut.

Its energy expert Stephen Murray said: "This is another example of energy companies failing to play fair with customers."

Mark Todd, director of comparison site energyhelpline, said: "The SSE price cut is probably the slowest in history, not coming into effect until the end of April, 95 days after its announcement."

SSE defended its approach, saying it was committed to prices "that are both competitive and stable".

"Its approach to buying energy in wholesale markets has enabled it to provide customers with more long-term certainty over its standard prices than any other energy supplier in Great Britain," it said.

"Although this can mean reductions to wholesale prices may take slightly longer to have an impact, customers know that they will benefit from price reductions without having to worry about prices going back up before July 2016."

SSE announced its tariff change as it delivered a trading update today, which revealed that it had shed nearly 400,000 customer accounts to 8.71 million in the nine months to the end of December.

Meanwhile it said the mild winter means average gas consumption per household fell by 15.8% over the period while electricity usage was off by 5.6%, adding that a "challenging business environment" was likely to continue.

However, shares rose 1% as it cheered investors by confirming that its full-year dividend would continue to rise by at least the inflation rate.

Energy firms are facing uncertainty ahead of the general election with Labour pledging to impose a price freeze.

The sector is also subject to a full-scale competition probe, with SSE today saying it expected further details to be published in the next few week and provisional findings in May or June.

SSE, which also trades as Scottish Hydro, Southern Electric, SWALEC and Atlantic, serves around four and a half million households.

Energy Secretary Ed Davey said: "It's good news for households when energy suppliers cut their prices and they should pass savings on to their customers whenever they can.

"But even greater savings are available if people shop around and switch supplier - over £300 in some cases."

Citizens Advice chief executive Gillian Guy said: "Pressure is clearly mounting on EDF to follow other suppliers and cuts its prices."

The French-owned firm said in a statement: "EDF Energy's prices are under constant review and we will always work to ensure that our prices attract new customers and offer good value to existing ones.

"Despite other suppliers recently cutting their standard gas tariffs, EDF Energy's existing prices remain very competitive."