Harmoni is commissioned by over 20 NHS PCTs to provide services for six million people including out-of-hours, GP-led health centres and urgent care centres.
It merges with Thamesdoc, a GP co-operative providing out-of-hours cover and other urgent care services to patients in Surrey and parts of West Sussex and Hampshire.
Andrew Gardner, Harmoni's chief executive, said: ‘This merger reinforces Harmoni's position as the market leader in the provision of urgent care services in England.'
Stephen Price, chief executive of Thamesdoc, said: ‘The recent Care Quality Commission interim report highlights the importance of delivering a high quality service where patient care and patient experience are the top priority.
‘We believe that this adds further weight to the move for out-of-hours providers to consolidate in order to have the scale to deliver the best patient care.'