This increase could lead to a more impressive year-on-year rise of 4-6 per cent in May, media buyers said.
The April increase would be a strong performance, coming on the back of an 8 per cent rise in April 2011.
April is expected to benefit from the presence of Easter and spending around the school holidays.
Meanwhile, brands seeking to avoid the Uefa Euro 2012 football tournament, as well as those advertising in the run-up to the competition, are likely to up their investment in TV in May.
Despite concerns around the economy and eurozone crisis, the TV ad market has held up in the first quarter and is expected to be flat against the first quarter of 2011.
It is understood that adspend on ITV1 is down between 3-5 per cent in the first quarter, against tough year-on-year comparables, but is expected to be higher than market increases in the second quarter of 2012 as Euro 2012 kicks off.
Channel 4's ad revenue haul is said to show healthy increases in quarter one because it did not trade with all the media agencies in January 2011. However, the broadcaster has underdelivered on some of its key audiences in February. Channel 5, meanwhile, is thought to be down around 6 per cent year on year after increasing revenues significantly in 2011.