President Donald Trump's approval rating has dropped below 50% according to a new poll by Fox News.

As the Republican nears his 100th day in office, his popularity has dropped slightly from the time he took office – with more than half of people surveyed stating he is failing.

The poll showed Trump currently has a 45% approval rating, down three points from the 48% approval rating he had on 20 January this year, and far lower than the previous two presidents' approval rating after 100 days in officer.

Former Democrat president Barack Obama enjoyed a 62% approval rating as he reached 100 days in office, while Republican George W Bush had a 63% approval rating at the same point, Fox reported.

As well as Trump's approval rating dipping, 44% do not believe Trump is keeping his campaign promises, although slightly more people (46%) believe he is sticking to his campaign pledges.

But more than half (51%) feel discouraged about the coming for years with Trump in charge, as opposed to the 45% who feel encouraged about Trump's time in office.

The Fox polls comes shortly after a Public Policy Polling survey that showed Trump's popularity at an even lower 40%, with 53% of people questioned in that poll stating they disapproved of him.

In particular, Trump's failed push to repeal and replace Obamacare did not go down well with voters, with polls revealing the Affordable Care Act is now more popular than it has been in its recent history.

"The main thing that this month's healthcare fight in Washington did was make Obamacare more popular than it's ever been before," said Dean Debnam, President of Public Policy Polling, in a statement.

"There's little appetite from voters to repeal it at this point."