Democrat Michael Dukakis campaigned for blue-collar votes in Michigan Friday and promised not to allow defense dollars to "line the pockets of Washington consultants." George Bush accused his rival of trying to hide a "far-left philosophy."

In Washington, President Reagan approved a 30-day extension of Secret Service protection for Jesse Jackson, at a cost Reagan's spokesman estimated at $600,000.Spokesman Marlin Fitzwater said the extension addressed Jackson's concerns about threats against his life but would not last through the fall campaign. "The feeling was that, first of all, he's not the nominee of the party," Fitzwater said.

Dukakis, reiterating his campaign pledge to work toward "full employment," made campaign appearances at two General Motors plants in Flint, Mich., a state that Jackson won in the primary campaign.

The Democratic nominee paid tribute to Jackson, saying after a private meeting with Jackson's Michigan supporters, "I want them; I need them; I want them to be a part of not only a great campaign but what I hope will be a great administration."

Speaking to 500 people outside a GM plant where Buicks are assembled, Dukakis took aim at Pentagon procurement practices, citing a recent report outlining abuses in the military acquisition program.

"We're not going to use our defense dollars to line the pockets of Washington consultants," Dukakis said. "In a Dukakis administration, we're not going to surrender our national security to greed and corruption."

Bush, meanwhile, stayed close to home, visiting a child-care center in a high-tech industrial park in Tyson's Corner, Va., to focus attention on his new $2.2 billion proposal to aid working families.

The vice president called his plan, which features a $1,000-per-child tax credit primarily designed for low-income working mothers, preferable to a $2.5 billion Democratic plan, endorsed in concept by Dukakis. The Democratic plan includes a more direct role for the federal government.

"You have to have choice, parental choice, family choice, and you have to have diversity," Bush said.

Dukakis, at a later campaign stop in Sturtevant, Wis., near Milwaukee, dismissed the Bush plan, saying, "I don't know of anyone who is seriously concerned about child care who thinks that makes sense."

However, his Democratic running mate, Sen. Lloyd Bentsen, said while campaigning at a day-care center in Los Angeles, "I think the Bush proposal is a step in the right direction, and I'm delighted to see them get aboard on this issue." He said of the Reagan administration, "They have not been very supportive of these kinds of efforts over the past eight years."

Bush told reporters the issues in the presidential campaign are still "all blurred out there right now."

"The Democrats had a good convention but offered no specifics," Bush said. "My opponent's suggestion that ideology doesn't matter just masks over his far-left philosophy."

Bush campaign manager Lee Atwater contended that the vice president's drop in the polls after the Democratic convention had just about bottomed out.

Bush planned to go on the offensive next week with speeches in Chicago on Tuesday and Corpus Christi, Texas, on Thursay on foreign policy and defense - an area in which the Bush campaign says Dukakis is the most vulnerable.

At the White House, meanwhile, presidential spokesman Fitzwater picked up on the same theme, accusing Dukakis of being "for a weaker defense."

Fitzwater spoke after a visiting West German conservative leader, Franz Joseph Strauss, said U.S. policy toward Western European countries will remain the same regardless of who is the next president.

The Dukakis campaign was quick to respond. "Marlin Fitzwater must be consulting the White House astrologer on Dukakis' position on defense," said senior Dukakis campaign adviser Kirk O'Donnell.

Bush said he hopes to make up his mind on a running mate before he leaves for the Republican National Convention in New Orleans Aug. 15-18. "We're going through some mandatory (background) investigations. . . . I think we're on schedule," he said.