He joins after working as a consultant at influential think tank Policy Exchange for three months, a role which he will continue alongside his MHP job.
Worth left his role as a senior political adviser in Downing Street in June, after two years working on a number of areas of public services reform. Previously he was head of the Conservative Party's policy unit.
Worth hit the news last year when it was reported that he was seconded to the Department for Health to help Health Secretary Andrew Lansley with his NHS reforms.
Gavin Devine, chief executive of MHP, said that Worth is ‘an acknowledged expert on politics and how policy is formulated’.
‘He is exactly the kind of bright, experienced person who can do smart thinking, and offer the best advice to really add value for our clients,’ he added.
Worth said: ‘MHP is renowned as a leading communications firm that adds genuine strategic value to its clients by virtue of a deep understanding of the audiences they seek to inform.’
MHP pointed out that, in line with the rules set down by the Government's advisory committee on business appointments, Worth will only offer strategic advice and will not lobby Government.
While MHP did not reveal how his time would be split between agency work and the Policy Exchange, a spokesman said that the arrangement ‘takes account of his existing commitments’.