Despite pledges to hold down federal spending to combat inflation. Congress so far has voted to boost fiscal 1974 government outlays by at least, $1 billion over the $268.7 bil- j lion budget ceiling proposed by President Nixon, a congres- j sional joint committee reported yesterday.</br></br>The figures, based on legislative actions completed through June 30, could provide ammunition for the White House in its battle with Congress over the budget. The White House has repeatedly j warned that the President will j employ vetoes and impoundments to stay under the ceil-i ing.</br></br>Compiled by the Joint Committee on Reduction of Federal Expenditures, the ?ÛÏbudget score-keeping report?Û? doesn?Ûªt give a complete picture, be-1 cause not a single regular appropriations bill has yet reached the White House although numerous supplemental funds bills and legislative-bills with impacts on spending have.</br></br>In passing the regular appropriations, Congress may well make cutfe deep enough to offset the increases already Vo^ed?ÛÓparticularly in defense, where Congress in recent years has regularly been cutting several billion dollars from the request.</br></br>Substantial cuts in defense outlays already appear to be in the works: A Senate Armed Services subcommittee has already recommended cutting $885.4 million out. of the $1.7 billion request for acceleration of the trident missile-firing submarine. This slash will delay completion of the first vessel by two years according to subcommittee chairman Thomas J. McIntyre (D-N.II.)