Northern Ireland Secretary Chris Heaton-Harris has been accused of "sabre-rattling" by Sinn Fein vice president Michelle O'Neill over his decision to ask civil servants to look at options for raising public revenue.Mr Heaton-Harris has written to Stormont permanent secretaries this week asking for information about revenue-raising measures such as domestic water charges, drug prescription charges and tuition fees, which he says will improve the sustainability of Northern Ireland's public finance

Northern Ireland Secretary Chris Heaton-Harris has been accused of "sabre-rattling" by Sinn Fein vice president Michelle O'Neill over his decision to ask civil servants to look at options for raising public revenue.Mr Heaton-Harris has written to Stormont permanent secretaries this week asking for information about revenue-raising measures such as domestic water charges, drug prescription charges and tuition fees, which he says will improve the sustainability of Northern Ireland's public finances.DUP leader Sir Jeffrey Donaldson also questioned the move, and said if it was designed to put pressure on his party to return to Stormont, it would not work.