Brazil's Serra widens lead in October race-poll

* Opposition Serra has 38 pct after last week's launch

* Ruling party's Rousseff has 28 pct, boosted by Lula

BRASILIA, April 17 (Reuters) - Brazil's main opposition candidate, Jose Serra, gained voter support in the October presidential race, widening his lead over the ruling Workers' Party's Dilma Rousseff, an opinion poll showed on Saturday.

Serra gained 2 percentage points to 38 percent of voter intention compared with the same poll a month ago, according to the survey published in the Folha de Sao Paulo newspaper.

Rousseff, who stepped down as President Luiz Inacio Lula da Silva's chief of staff nearly three weeks ago, gained 1 point to 28 percent.

It is the first poll since Serra launched his campaign a week ago, representing the three main opposition parties, including his own centrist PSDB.

The Serra camp will likely celebrate the results after an opinion survey by polling firm Sensus this week had shown Dilma moving into a virtual tie with the better-known Serra, who stepped down as Sao Paulo state governor this month in line with electoral law.

Former environment minister Marina Silva of the Green Party jumped 2 points to 10 percent of voter intention and former Ceara state Governor Ciro Gomes lost 2 points, falling into last place with 9 percent, the Datafolha poll showed.

Rousseff, 62, has benefited from Lula's huge popularity ratings of around 80 percent and by a fast-recovering economy.

Serra, aged 68, is highlighting his executive experience as former mayor of Sao Paulo, as well as stints as health minister and planning minister under Lula's predecessor, Fernando Henrique Cardoso.

Neither of the two leading candidates would break with the fundamentals of Lula's mostly market-friendly policies. Both are seen as favoring a stronger government role in the economy.

The survey polled 2,600 people April 15-16 and has a margin of error of plus or minus 2 percentage points.

(Reporting by Raymond Colitt; Editing by Doina Chiacu)