The Cordiant Communications-owned agency worked on most of last month's biggest deals, including client Network Rail's £7bn bid for Railtrack, announced at the end of March.
FD also picked up the City PR brief for Thames Water parent RWE and its £5.2bn offer for Innogy, the UK's largest electricity supplier (PRWeek, 29 March).
Meanwhile, the agency this week confirmed it had appointed Chris Hughes, investment reporter at The Independent, as an associate partner in its financial team, reporting to director Alex Child-Villiers.
The Maitland Consultancy ranked second in the table, gaining seven places since February, largely due to its work for Railtrack, which appointed the agency in place of Brunswick last October.
Despite working on more deals than any other UK City PR firm, Brunswick slipped down to third place after four months in top spot.
The consultancy handled PR for 14 deals, notching up £7.9bn, including client Imperial Tobacco's £3.2bn acquisition of its German counterpart Reemtsma.
Brunswick also advised private investor bid vehicle First Aqua on its £2bn takeover of Southern Water.
Tulchan Communications joined Brunswick on the deal, working on behalf of retained client Scottish Power - Southern Water's parent group.
The deal saw Tulchan enter the Deal Watch top ten for the first time in two months, bagging fifth place.
The Hogarth Partnership also made a return to the league after seven months absence.
Last month's completed £559m sale of the Regional Independent Media Group (RIMG) to Johnston Press helped move GCI Financial up one place to ninth position, working on behalf of RIMG parent Candover Investments.
Citigate Dewe Rogerson scraped into the league in tenth place, mainly due to its work for client Legal & General Ventures.
Deal Watch, compiled according to publicised deals involving at least one UK company, reveals deal figures are up on previous months, with the top takeover worth more than double that in February.