Investment in TV drama has fallen by 44% since the last review in 2008.
The report found that "the drops in the levels of investment, particularly on ITV, are a concern".
The media watchdog's review found spending on children's programmes in the UK had also fallen from £103m in 2008 to £88m in 2014.
The BBC now accounts for 97% (£84m) of total public service broadcasting spending on children's programmes.
Spending by ITV, Channel 4 and Channel 5 on children's TV has dropped by 74% to £3m in 2014.
The review points out there is "very limited provision of non-animation programming beyond the BBC".
The review found that, despite the success of big budget dramas like Downtown Abbey and Doctor Who, the amount of new UK drama being shown on the main channels has fallen from 627 hours in 2008 to 371 hours in 2014.
Although it noted that "audience satisfaction with drama is stable".
The review found that - following the removal of specific quotas in 2003 - public service programmes in arts and classical music, religion and ethics, and formal education has significantly reduced.
Ofcom also warned broadcasters need to adapt as the trend towards online viewing grows.
The watchdog found that unless the main TV channels adapt their business models, they would struggle to pay for public service programming in the future.
Ofcom warned another challenge for the broadcasters in the future will be delivering news to younger audiences, as viewing of TV news has fallen by 29% among people aged 16-34.
It also found certain audience groups were concerned about how they were portrayed on screen - particularly people from BAME backgrounds or people with disabilities - either being under-represented or unfairly portrayed.
However, the review found that general audience satisfaction  was high with 79% believing PSB was delivering on its purposes, such as delivering trustworthy news and high quality programming reflecting the UK.
That figure is up from 69% in 2008.
The review also found PSB channels continue to make a significant contribution to UK broadcasting.
In 2013, they invested just over £2bn in new UK programmes, not including sports content, compared to around £350m from non-PSB companies.
The main UK TV channels, BBC, ITV, STV, UTV, Channel 4, Channel 5 and S4C, all carry programmes with public service values.
Over half of all TV viewing is on these main channels - but that figure rises to more than 70% when the time shifted channels are taken into account.
An Ofcom review into public service broadcasting (PSB) in the UK has raised concerns about a fall in spending on drama and children's programming.