Senior managers have been ordered to take a 'personal lead' in reducing Welsh waiting lists.
In a letter to trust and health authority chairs, new health minister Jon Owen Jones said a 'fall-off in performance' revealed last week was 'unacceptable' and year-end targets must be met.
Figures from the Government Statistical Service showed the number of Welsh patients waiting for inpatient treatment rose by 1,700 to 75,100 between March and June this year.
The number waiting more than 12 months rose from 8,000 to 9,300 and the number waiting more than two years rose from 306 to 496.
'I will be making arrangements for an early meeting with some of you to discuss your plans and my expectations,' said Mr Jones in his letter, copied to chief executives.
He said that 'most' of the extra 25m secured for the NHS in Wales in the Budget had been allocated to HAs to reduce waiting lists.
But Allister Stewart, chief executive of University Hospital of Wales trust and chair of the Institute of Health Services Management in Wales, said it had 'only come through in the past few weeks', whereas in England it 'kicked in earlier'.
'The real difficulty will be dealing with these patients over the winter, when a lot of emergency work comes in,' he said.
Last week's figures also show that the number of people waiting for a first outpatient appointment in Wales leapt by 19,300 to 130,100. The number waiting more than six months increased by 4,300 to 13,900.
Fiona Peel, chair of the NHS Confederation in Wales, said HAs and trusts were 'not satisfied' with the overall figures and would reduce them. However, she said the service, which is in the middle of a trust reconfiguration programme, needed 'stability' to tackle the problem.
Marcus Longley, associate director of the Welsh Institute of Health and Social Care, said the overall rise was attributable to emergency and financial pressures and a 'lack of emphasis' on cutting waiting lists before Mr Jones arrived in this summer's ministerial reshuffle.
'This has not been an imperative,' he said. 'It obviously is now.'
NHS Wales: hospital activity and waiting lists: 30 June 1998. Government Statistical Service. 01222-825016.