England need to find the right T20 formula, says Ashley Giles

England limited-overs coach Ashley Giles is searching for the right "formula" ahead of the Twenty20 World Cup in Bangladesh after his side suffered a series defeat against the West Indies.

England have been below par during the three-match Twenty20 series in the Caribbean, with the West Indies comfortably wrapping things up after victories in the first two games.

A lack of impetus from England's top-order batsman has played its part in their downfall. Giles's side have lost all five of their T20 fixtures in 2014.

"Clearly we're not playing very good Twenty20 cricket, and we haven't done for a period now," Giles told Sky Sports before England's final T20 match against the West Indies on Thursday.

"We've got good personnel and we've got to find a formula in that top three. We back these guys to do the job."

England, who won the World T20 in 2010, travel to Bangladesh straight after the third T20 against the West Indies, with the tournament starting on March 16.

"We are going to try and win the tournament," Giles said. "But, realistically, we are eighth in the world rankings, we've not played well at all over the last year, so we are the underdogs.

"Sometimes that's a good place to be, but at the moment it doesn't feel like that."

Giles, who is in contention to become the next head coach of England's Test side, wants his players to take the shackles off against West Indies on Thursday as they try to find some form.

"Our message is, quite clearly, 'go and express yourselves, we back you, go and play your way'," he said.

"But I think, as much as you say that, you have to understand that guys who are struggling for runs - in the heat of battle, with options going through their head - are sometimes going to hesitate.

"If you slightly back off that option, choice, decision you're going to get into trouble."