The net appears to be closing in on the UK's big utilities - as ScottishPower has been banned from recruiting new customers for 12 days by the regulator.
Ofgem said the power group - one of the big six - had failed to clear up outstanding Ombudman's decisions by the end of November - the month that the watchdog launched the investigation into the group's treatment of customers.
The ban comes into effect from today (Wednesday).
The group had agreed to meet three targets put by the regulator, including reducing the amount of time people are left waiting on the phone and cutting the number of overdue bills to 75,000 to 30,000 by the end of the year - two which it met.
But it failed to remove the ombudsman backlog by the end of November.
Chief Ombudsman Lewis Shand Smith said the organisation strongly supported the sales ban.
It had been "calling for action to be taken on this for several months".
"The proportion of energy complaints that we receive related to Scottish Power is high and we welcome the company's stated intention to get its house in order," it said.
The UK energy sector is facing considerable pressure form several quarters.
Earlier this year, the Competition and Markets Authority (CMA) found customers were missing out on big savings by not switching suppliers and that established 'Big Six' dual fuel customers on standard tariffs could have saved between £158 and £234 a year.
The big six firms are SSE (LON:SSE), Scottish Power, Centrica (LON:CNA), which owns British Gas, RWE Npower, E.On (LON:E.ON) and EDF Energy.
SSE shares eased 1.4% to 1,54p, while Centrica (LON:CNA), added 0.57% to 248.9p.